QUEER LIFE IN EUROPE DURING THE SECOND WORLD WAR

Régis Schlagdenhauffen

Book Chapter published in Régis Schlagdenhauffen (ed.) Queer in Europe during the Second World War, Strasbourg, Council of Europe, 2017, pp. 7-20. Following on from the Roaring Twenties, and despite the economic crisis, the 1930s began with a relatively carefree attitude towards homosexuals in Europe. Nearly every town had music halls, dance halls, bars and discreet cafés that were also meeting places for men who liked men and women who liked women. Across the continent, thanks to advances in transportation, homosexual tourism continued to increase from the Mediterranean to the Baltic, via the Atlantic and the North Sea. Lesbianism was not to be outdone, and the year 1931 was marked by the huge success of Mädchen in uniform (Girls in uniform), the first commercial lesbian film in the history of cinema, directed by Léontine Sagan. More generally, times were changing, especially sexually. The World League for Sexual Reform, founded in 1928 by a sexologist from Berlin, Magnus Hirschfeld, sought to have a progressive influence on the governments of European nations. The League demanded that they have "a rational attitude towards sexually abnormal persons and especially towards homosexuals, men and women" [START_REF] Tamagne | La Ligue mondiale pour la réforme sexuelle : la science au service de l'émancipation sexuelle?[END_REF]. However, the ideas conveyed by the reformists were soon jeopardised by the rise to power of extremist parties that announced the advent of totalitarian regimes in Europe.

The wind changed in several countries from 1933. Sexuality, particularly homosexuality, was again a focus of debate [START_REF] Domeier | The Eulenburg affair. A cultural history of politics in imperial Germany[END_REF][START_REF] Praetorius | Die Homosexualität in den romanischen Ländern[END_REF][START_REF] Schlagdenhauffen | Retour sur une controverse franco-allemande : l'Affaire Paris-Berlin (1904-1914)[END_REF]. As had been the case on the brink of the First World War, homosexual scandals broke out and were used for political gain. In France, the Dufrenne Affair, from the name of a theatre director found dead in 1933 and whose killer was suspected of being a male lover (Tamagne 2006a), illustrates the shift that occurred during this period: the homosexual, associated with feminine traits, embodied the nation's decline. The "inverts", as they were called, symbolised treason and justified the urgent need for a moral turnaround. In Germany, the young Marinus van der Lubbe, who was allegedly homosexual and an anarchist communist, was accused of setting fire to the Reichstag in February 1933. He was sentenced to death for high treason. On 6 May, it was the turn of the Institute of Sexology, founded by Magnus Hirschfeld in 1919 in Berlin, to be destroyed by the Nazis as part of the operation against "non-German" thinking (Schlagdenhauffen 2005: 155-7). The following summer, Ernst Röhm, the openly homosexual chief of staff of the Sturmabteilung (SA), was assassinated during the Night of the Long Knives (June 1934). Immediately afterwards, roundups and arrests of homosexuals multiplied across the whole of Germany. More repressive legislation followed with, in June 1935, an increase in the severity of paragraph 175 of the German Criminal Code, whereby all types of homosexual relationships between men were punishable by sending the perpetrators to concentration or re-education camps, effective immediately. In the Soviet Union, the crime of sodomy, abolished in 1917, was reintroduced in 1934, making homosexuality punishable by five years in a forced labour camp (gulag). In Italy, the chief destination of exiled German and Austrian homosexuals, Mussolini also authorised in 1938 the arrest of homosexuals and their imprisonment on the Isole Tremiti in the Adriatic Sea.

During the interwar period the condemnation of homosexuality was predominantly focused on men. Ways of expressing disapproval of female homosexuality were more subtle and less common, especially as a result of the gender hierarchy, whereby it was deemed that women, if they were lesbians, would cause less harm to the nation and to patriarchy.

Up to now, the period of the Second World War has constituted a parenthesis in research into homosexuality. The late 1930s and the early 1950s are two chronological milestones separating, on the one hand, an initial homosexual movement born in 1897 [START_REF] Lauritsen | The early homosexual rights movement (1864-1935[END_REF], which reached its peak in Germany in the interwar period, and, on the other hand, a homophile movement born in the post-war period in several European countries, which entered into a decline from the 1970s [START_REF] Bech | A short history of gay Denmark (1613-1989)[END_REF]Hekma 2004;[START_REF] Jackson | Arcadie. La vie homosexuelle en France de l'après-guerre à la dépénalisation[END_REF]). The scarcity of information sources on sexuality, particularly homosexuality during the Second World War, partly explains this lack of research into homosexuality and homosexuals during this era, with the exception perhaps of the work done concerning homosexuals in Nazi concentration camps (Mußmann 2000).

Sociosexual context during the Second World War

Between 1939 and 1945, millions of Europeans were drawn to having pre-marital and extramarital sexual encounters, shifting their own moral boundaries and experiencing relationships that would have been quite simply impossible and unimaginable in times of peace (Herzog 2011: 98). Some historians claim that the Second World War, more so than the First World War, created new erotic situations that facilitated homosexual practices and encouraged the development of gay and lesbian identities after the war (D'Emilio 1990).

Firstly, the social and cultural context in question was characterised by the increased repression of homosexuals in several European countries, starting with Germany and the territories that it gradually annexed, while an attitude of detachment towards homosexuality prevailed in the occupied territories both in the west and the east. Secondly, the types of sexual engagement and encounters that the Second World War engendered were often described after the fact, using terms such as "circumstantial" or "situational". Presented in this way, homosexual experiences became comprehensible and excusable and were regarded as a stopgap for the out-of-reach heterosexual relationship. The aim of this book is to go beyond such preconceived ideas and to show that, between 1939 and 1945, the issue went beyond that of identities and sexual experiences, because it became a political issue. In parallel with the subjective experiences of homosexual affairs and relationships, some European states picked up on the homosexual question, criminalising or decriminalising it; they initiated policies that would continue into the post-war period and allow us to understand, in the end, why our continent is today a forerunner in the fight against homophobia and discrimination.

By opening up debate on a different history, one that was indeed marked by repression but also by enlistment in armies at war, collaboration, and resistance in underground networks, the aim of this work is to explore these different situations while taking into consideration the temporalities of the conflict and national specificities. By jointly addressing these aspects, we are able to shed more light on the question of homosexuality in time of war and at a European level. In the first part of this book, the contributions will discuss the types of repression used against homosexuals, firstly in Germany, then in Austria, where lesbianism was suppressed to an extent incomparable with what happened elsewhere in Europe. In the second part, the authors evoke the situations prevailing in areas annexed during the war, in order to show how territories attached to the Third Reich were brought to heel. A study of the dismantlement of Czechoslovakia from 1940 on will make it possible to understand how several types of controls over sexuality were put in place. The example of the annexation of Alsace-Moselle will demonstrate how the integration of these regions into the Reich went hand in hand with the gradual exclusion of homosexuals from Alsace and Moselle. In the third part, the main focus will be homosexuality under an authoritarian regime: whether Hungary under Horthy, Italy under Mussolini or the Soviet Union under Stalin, these three examples will make it possible to understand how the temporalities of the war affected a group of individuals whose ostracism was conceived as a political tool. In the last section, this book will discuss on the one hand the situation in Sweden to understand how decriminalising homosexuality at the end of the Second World War was the first sign of the reforms that would affect all of Europe during the second half of the 20th century. On the other hand, it will discuss the situation in Yugoslavia: more precisely, how the anti-fascist movement dealt with homosexuality.

To write such a history at a European level, it is moreover necessary to put this issue back into the context of European historiography of the Second World War, which has paid scant attention to homosexuals because, after the war, few people were interested in them.

From the 1970s, the development of social movements for the liberation of women, gays and lesbians on both sides of the Atlantic, and the greater attention paid to victims of persecution, created a twofold dynamic. On the one hand, young people engaged in gay and lesbian emancipation movements sought to rebalance the writing of a history from which they felt excluded; on the other hand, activists searched for homosexual survivors and veterans from the Second World War with the aim of eliciting their testimony and consequently contributing to nourishing a collective memory. This dual movement was part of two broader dynamics that were "the era of the witness" and "competition between victims" [START_REF] Wieviorka | L'ère du témoin[END_REF]Chaumont 2002). Then, during the 1980s, at the same time as the emergence of the HIV/AIDS epidemic, people following the example of Guy Hocquenghem went on to assert that homosexuals had been victims of a genocide, of a "gay holocaust"1 during the Second World War. University research and non-university research carried out from the 1980s on was focused above all on the fate of homosexuals in Nazi concentration camps. It showed that a systematic persecution did not take place on a European level [START_REF] Tamagne | Histoire des homosexualités en Europe : un état des lieux[END_REF]). The research in question, quite often conducted locally, was primarily motivated by the desire of gay and lesbian organisations to show associations of former deportees that homosexuals had also been victims of the Nazi regime and, as such, they deserved to benefit from symbolic recognition in official commemorations. The historiography of homosexuals during the Second World War therefore has a political dimension, in that it constitutes a dynamic process permitting a social group that had long been kept silent to speak out and become visible. More generally, it is part of the history of homosexualities, which lies at the intersection of the history of sexualities and the history of genders, in that it concerns both the masculine, the feminine and the intrinsic hierarchies of each gender.

European homosexuals during the war

During the war, neutral Switzerland was seen as a beacon in the darkness. Le Cercle, an organisation based in Zurich and founded in 1932, was the only homosexual association to remain active. Its eponymous newspaper played a key role because it allowed homosexual people from all backgrounds to stay connected during the conflict [START_REF] Kennedy | The ideal gay man: the story of Der Kreis[END_REF]). However, homosexual organisations and associations formed only the most visible part of European homosexual subcultures. Many homosexual men and women, sometimes as couples, sometimes single, were able to continue leading a safe and discreet life during the war. They were simply subjected to the same restrictions as the rest of the population and, for the most part, there is little trace of them in the archives. Nevertheless, the temporalities of the war transformed means of movement between urban and rural zones, just as they affected the hierarchies between urban areas. At times, homosexuals found themselves confined to areas, leaving few possibilities for movement. The fact that it became impossible to "go into town", a traditional place for more or less anonymous sexual encounters, forced a number of them to express their desires in ways that they would not have considered during times of peace. However, the archives contain only scant information on informal homosexual sociability. It is also a challenge to uncover this information, since it involves gathering coherent sources on a population that is, above all, defined by its sexual practices, whether criminalised or not, and perceived differently according to the locations concerned. Sometimes it is necessary to resort to verbal sources and personal documents, such as diaries. The diary belonging to the bisexual lawyer Eugène Wilhelm , for instance, reveals the transformation of sexual practices and fantasies during the Second World War. After withdrawing to the countryside following the evacuation of the French border zones, he described in these words the encounters he had with one of his young lovers: More generally, the small amount of research carried out on homosexuality in rural areas has shown that gays and lesbians actually had a large choice of meeting places, sometimes semipublic, sometimes private, making it possible for them to have sex. 4 British historian Emma Vickers (2011) has gathered many oral testimonies from British gay and lesbian veterans who, during the Second World War, had sexual encounters behind the front lines or on trains. Other testimonies attest to traumatic experiences on trains, especially when a homosexual identity was synonymous with disgrace. Heinz Heger, known as one of the first deported homosexuals to have testified in the 1970s, states in his memoirs that he was raped on a train that was taking him to a concentration camp.

Homosexual behaviour did not only occur in the countryside and on public transport during the war. In many towns, public toilets and walkways maintained their social function as meeting places. In Prague, galleries, public baths and cafés welcomed the same clientele, putting aside the war and its unpleasant consequences. However, the war entailed several changes with regard to how homosexual communities functioned. In Czechoslovakia, the establishment of the Protectorate (16 March 1939) led to the dissolution of the army. Soldiers who were used to prostituting themselves in uniform were quickly replaced by young men enticed by the money involved. Very often forced into prostitution for economic reasons, they often turned out to be skilled blackmailers. As shown in Jan Seidl's contribution to this book, this led the police to focus their attention on male prostitution networks, which they were seeking to dismantle, rather than on homosexuals. In Italy too, the occupation of the south by Anglo-American troops from 1943, combined with the growing destitution of the local population, encouraged the development of a new type of prostitution, which turned Naples into a "big brothel" (Le [START_REF] Gac | Le mal napolitain : les Alliés et la prostitution à Naples (1943-1944)[END_REF] or even, if one is to believe the Italian writer Curzio Malaparte, the new European capital of homosexuality [START_REF] Malaparte | La pelle[END_REF]. Lastly, in the Soviet Union, the practice of homosexuality was unimpeded, albeit discreet. Nevertheless, throughout our war-stricken continent, to engage in a homosexual relationship was rarely without risk.

Homosexuals and the law

Wartime can be a period conducive to legislative changes, particularly with regard to moral standards. Three distinct positions can be noted: the states that maintained the status quo regarding homosexuals, those that strengthened their legislative arsenal and, lastly, those that relaxed it.

As shown in the contributions by Arthur Clech, Johann Karl Kirchknopf and Régis Schlagdenhauffen, Germany, Austria, Romania and the Soviet Union retained existing legal provisions. In fact these states had tightened their criminal codes before the war. The USSR had recriminalised homosexuality in 1934, Germany had increased the severity of paragraph 175 in 1935 and Romania had introduced the concept of acts of sexual inversion when reforming its Criminal Code in 1937. 5 Nevertheless, it would be inaccurate to say that nothing changed with the advent of war. In Germany, on 12 July 1940, a Nazi decree ordered the immediate internment in concentration camps of all men who had been found guilty of homosexual seduction. Then, in 1942, Hermann Göring decreed that a number of homosexuals be "put to the test" after serving their sentences. This measure ultimately led to homosexuals being enlisted in the Wehrmacht at a key moment in the conflict. Following the Anschluss, Germany required Austria to amend its interpretation of the Criminal Code to bring it into line with paragraph 175.

France was one of the countries that, on its own initiative, reinforced its legislation during the war. While homosexuality had no longer been punished since the French Revolution, Marshal Pétain approved, on 6 August 1942, a law introducing the concept of an "unnatural" act into French law. This change illustrates the moral crusade led by the Vichy regime, which had set out to regenerate the nation (Jackson 2009: 45). Admittedly, the law only sanctioned homosexual relationships between an adult and a minor over 15 years old, but it nevertheless led to the prosecution of victimless offences.

In the annexed Alsace-Moselle regions, German law was introduced from January 1942. Soon after, the number of arrests escalated and the judgments handed down show that the courts took a hard legal stance with regard to homosexuals from Alsace and Moselle. Nazi justice also adopted the principle of the retroactive application of the law. In concrete terms, this meant that men could be sentenced for acts committed at a time when homosexuality was not an offence. In a case tried in mid-1944 in Strasbourg, the court referred explicitly to the principle of retroactivity applicable in Alsace so as to be able to flesh out the evidence against a defendant prosecuted for "unnatural relations with men", because he was accused of having caressed the leg of a soldier. Following his arrest, and during the interview, he admitted to having already masturbated with another man, two or three times at most, before the war. This made it possible for the court to consider him as a repeat offender. He was sentenced to six months in prison (Schlagdenhauffen 2014: 100).

The law was also applied retroactively in the Sudetenland, a region annexed by Germany since 1938. 6 This provision enabled the arrest of 210 homosexuals in 1941, 112 in 1942 and 48 in the first half of 1943.

In situations of occupation, the occupying power could amend the provisions in force, along the same lines as what had happened in Austria following the Anschluss. The occupation of the Netherlands led to the overlap of two sets of rules. In addition to the Article 248 bis , of the Dutch Criminal Code which specifically condemned homosexual relations between adults and minors over 15, the Order No. 81/40 was promulgated by the occupying army on 31 July 1940. It made male homosexual relations punishable by a five-year prison sentence. From a formal standpoint, this order was nothing other than an exact copy of the German paragraph 175. However, since the Dutch police were not very co-operative, few charges were brought. Between 1940 and1943, 138 men were brought before the courts pursuant to Order No. 81/40: 90 were sentenced, including 54 who were given a prison sentence and 10 who were committed to psychiatric hospitals. At the same time, 164 men appeared before the courts for violation of Article 248 bis .

In Hungary, the government of Miklós Horthy adopted another type of treatment for homosexuals. Archives investigated by Judit Takács show that the Hungarian security services drew up lists of homosexuals, and 992 of them were considered fit for forced labour, in the same way as the Jews and political dissidents.

In Poland, a country that had decriminalised homosexuality in 1932, the traces of just a single case during the occupation have been found, attesting to the lack of German interest in the repression of homosexuals outside of the Reich. A Polish man who maintained a relationship with a German soldier was arrested in 1942. He was sentenced by the court of Torùn, managed by the occupying forces, to five years' imprisonment for violating paragraph 175.

Poland was not the only country to have decriminalised homosexuality before the war, since Denmark had done the same in 1933. This situation differs from that of countries that decriminalised homosexuality during the war. Iceland was the first of these in 1940, followed by Switzerland in 1942. In Switzerland, the German-speaking cantons had, until then, tended to punish homosexuality following the principle of paragraph 175, whereas the French and Italian-speaking cantons mainly drew on French or Italian law, which did not punish homosexuality. However, the decriminalisation in 1942 did not apply to the Swiss armed forces, due to the fear of the potential impact of homosexuality on troop morale [START_REF] Delessert | Les homosexuels sont un danger absolu : homosexualité masculine en Suisse durant la Seconde Guerre mondiale[END_REF]. The last European country to decriminalise during WW2 was Sweden in 1944. As Jens Rydström points out in the chapter devoted to this country, the argument put forward by reformers was the need to restrict opportunities for blackmailers who preferred to target homosexuals.

With regard to the risks run by those arrested for homosexuality, the majority of countries imposed prison sentences or internment in forced labour camps. Historical research carried out on the Gulag and concentration camps has shown that closed institutions of this type encouraged the development of a subculture, inspired partly by the prison subculture and very hostile towards homosexuals. To a certain extent, the subculture concerned was reflected in camp jargon, in which every term used was part of a hierarchical system classifying the individuals concerned. In Russia, the terms pidory (passive homosexual), kobly (a woman playing the role of a man) and kovriyalki (a woman who plays the role of the woman), used in the gulags, contributed to the formation of a gender hierarchy (Kunstman 2009).

In Nazi concentration camps, a visible pink triangle was the "homosexual" badge, which was a symbol that allowed homosexual men to be distinguished from other prisoners. Introduced in 1937, it was only used for prisoners of the Reich. 7 The number of those who wore it in the camps never exceeded 1% of a camp's total population. Despite their small number, homosexuals were seen as repellent individuals. One of the rare options for homosexuals to escape their deadly situation was to be integrated into the Wehrmacht. This last point leads on to the question of homosexual participation in the war.

Homosexuals serving in the armed forces during the war

Following the Swiss example, many armies considered homosexuality strictly incompatible with rough soldierly manners [START_REF] Rosario | Homosexuality and science. A guide to the debates[END_REF]. Under British Army instructions this was a clear reason for exclusion [START_REF] Jackson | One of the boys. Homosexuality in the military during World War II[END_REF]. The majority of homosexuals serving in the armed forces were aware of this and chose to hide their sexual orientation. At the same time, this explains why the cases of homosexuality to be found in public archives mostly concerned circumstantial or compensatory homosexuality (Delessert 2012: 80 ff.).

According to [START_REF] Vickers | The good fellow: negotiation, remembrance and recollection -Homosexuality in the British armed forces, 1935-1945[END_REF], homosexuals kept a particularly "low profile" in the army and this is why few veterans are able to confirm that they encountered homosexuals during the war. However, many of them joined up, either through conscription or voluntarily. Vickers cites Peter Tatchell as claiming that around 250 000 gays served in the British armed forces (2011: 115). This number contrasts with the 790 cases of "indecency" brought before the British Court Martial between 1939 and 1945. 8 According to [START_REF] Vickers | The good fellow: negotiation, remembrance and recollection -Homosexuality in the British armed forces, 1935-1945[END_REF], the low number of cases reported was linked to the camouflage strategies deployed by homosexuals. However, going undercover did not mean that their sexual orientation would not eventually be discovered. The Croatian historian Franko Dota (2012: 22) has researched the case of the 7 . Testimonies state that lesbians had to wear black "asocial" triangles, since the legal provision that sanctioned "unnatural relations" applied only to men in Germany. See Schlagdenhauffen (2011). 8 . Section 11 of the Criminal Law Amendment Act 1885, Labouchere Amendment, in The War Office (1950).

Partisan Josip Mardešic. As a Captain in the Yugoslavian National Liberation Army, he was charged with homosexuality and brought before the Supreme Court in March 1944, whereupon he was sentenced to death and executed. 9 According to Dota, the chargesseduction of subordinates, unnatural sexual relationships with persons under his authority, corruption of young persons causing irreparable damage to their normal developmentdemonstrate the puritan stance taken by Yugoslavia towards homosexuality, considered to represent a danger to both the nation and the army.

The emphasis on aggressively heterosexual masculinity in the military did not necessarily mean that homosexuals were not enlisted. Nazi Germany is a textbook case. Until 1943, cases of homosexuality in the Wehrmacht were systematically punished but did not lead to the exclusion of homosexuals; they were incorporated into penal battalions. 10 According to the historian Hans-Peter Klausch (1993: 24), this strategy was aimed at bringing these men back onto the right path, that of heterosexuality, because expelling them from the army would have sent a strong signal to all those who were trying to evade their military obligations (ibid.: 24). 11 For this reason, the Wehrmacht preferred to retrain homosexuals rather than exclude them. Franz Seidler (1977: 201) adds that "even emasculated men were still fit for military service, as long as they were worthy of serving (Wehrwürdig). It was not desirable to dispense emasculated men from their military obligations". From 1944, when Germany was experiencing huge and growing losses on the eastern front, it was decided to resort to the forced incorporation of homosexuals interned in concentration camps, as Schlagdenhauffen describes in his contribution. A number of testimonies show that this political strategy was seen as a last hope. The historian Rainer Hoffschildt (1992: 130-3) has retraced the career of Heinz F., one of the last homosexuals to have been forced into the army. On 1 May 1945, eight days before the capitulation of Nazi Germany, he joined the Wehrmacht under duress. 12 What about the homosexuals engaged in clandestine forms of combat and in the resistance movements that developed in several European countries? The research remains incomplete on this sensitive issue that, according to Gilles [START_REF] Perrault | Dictionnaire amoureux de la Résistance[END_REF], is a "taboo within the taboo".

In France, several homosexual men and woman were engaged in resistance networks from the outset, including Pascal Copeau (who was one of the founders of the National Council of the Resistance) and the lesbian artist Claude Cahun, who actively participated, with her partner, in resistance movements on the island of Jersey until she was arrested by the Gestapo in 1944.

Seidl has also discovered evidence of Czech homosexuals who participated in resistance networks. A network was established around a priest, Otakar Zadražil (1900-45), from the Augustinian Monastery in Brno. Women also set up a network in Prague by establishing a network in which all of the members (men and women) were homosexual. Vague sources attest to the fact that this group was arrested and deported as political prisoners (Seidl et al. 2014: 263-4).

In addition, in the concentration camps homosexuals played a key role in the internal resistance networks. As Tamagne (2006c) points out, Robert Oelbermann, one of the leaders of the youth movements prohibited by the Nazis, was accused of an offence under paragraph 175 and sentenced in September 1936 to 21 months of forced labour. He was then transferred to Sachsenhausen concentration camp:

With Rudi Pallas, a former scoutmaster (Pfadfinder), he organised a resistance group that was able to unite deported homosexuals and politicians in Sachsenhausen. Rudi Pallas, who was released in May 1940 and forced to serve as a medical officer on the Eastern front before being captured by the Russians, continued his resistance activities in prison. After the war, he was one of the few deported homosexuals to receive the title "victim of war" in light of his political engagements. (ibid.) 13 A history of sexuality, and therefore of homosexuality, in the resistance still needs to be written. That would shed new light on the issue of homosexuals who collaborated, a subject that generally arouses considerable interest [START_REF] Anglebert | Eros en chemise brune. La face cachée du nazisme[END_REF]. Certain of these collaborators are known, such as the far-right writer and journalist Robert Brasillach [START_REF] Kaplan | Intelligence avec l'ennemi : Le procès Brasillach[END_REF] or even Abel Bonnard, member of the French Academy and Minister of Education under Vichy, who was nicknamed "Gestapette". Hiding in Spain at the end of the war, he was found guilty of collaboration, sentenced to death in absentia and expelled from the French Academy.

Homosexuals after the war

The immediate post-war period was initially marked by the reconstruction of a Europe left devastated and grieving and then divided by the Cold War. This period, which saw stable institutions established on the continent with a view to a lasting peace -starting with the Council of Europe in 1949 in Strasbourg -was not necessarily more favourable for homosexuals. In a majority of countries, the legislation in force during the war was retained [START_REF] Judt | Postwar. A History of Europe since 1945[END_REF]. In Germany, paragraph 175 remained in place, leading to the conviction of more than 50 000 homosexuals between 1949 and 1969. In the United Kingdom, the police were particularly active in repressing homosexual relationships between men at the end of the 1940s and during the 1950s [START_REF] Bauer | Queer 1950s. Rethinking sexuality in the postwar years[END_REF]. However, the repression of homosexuals after the war did not take place solely in the aforementioned countries, since the same observation has been made concerning other nations with a reputation for greater tolerance, such as the Netherlands, Denmark, Norway and Finland (Rydström and Mustola 2007;[START_REF] Koenders | Tussen christelijk réveil en seksuele revolutie. Bestrijding van zedeloosheid in Nederland, met nadruk op de repressie van homosexksualiteit[END_REF]). 13 . See Sternweiler A. (2000), "Homosexuelle aus der Jugendbewegung", in Müller J. and Sternweiler A. (eds), Homosexuelle Männer im KZ Sachsenhausen, Schwules Museum Berlin, Verlag rosa Winkel, Berlin, cited by Tamagne (2006c).

At the same time, there was an increased interest in the psychiatrisation of homosexuality and homosexuals, particularly thanks to the development of electroconvulsive therapy. To paraphrase Delessert, psychiatric facilities replaced criminal justice and the "criminals" were transformed into mental patients (2012). The cases considered by doctors to be the most serious were also subject -as in the United Kingdom -to "voluntary castration", which was only voluntary in name. This finding is not confined to western Europe; in eastern Europe, particularly in the USSR, homosexuals underwent psychiatric assessment. Based on his ongoing research, Clech writes that, in the Soviet Union, half of the lesbian women whom he interviewed claimed that at least one of their partners or acquaintances was sent to an asylum after 1945. Psychiatric hospitals were therefore assigned a preventive function, but also one of re-education, which was hardly different from the function previously carried out by detention centres.

All in all, the post-war years in Europe were marked by a fresh outbreak of police repression, and social and medical stigmatisation of homosexuals. The liberation of homosexuals would only take place from 1969 onwards thanks to the gradual appearance of a gay and lesbian movement, then the lesbian, gay, bisexual and transgender (LGBT) movement.

  Thursday 7 September 1939, I made love to Jean in the bushes. (Wilhelm 1939a) 2 Tuesday 19-Thursday 21 December 1939: Back to full health … Made love to Jean in the forest." (Wilhelm 1939b) 3

. See the preface written by Guy Hocquenghem in[START_REF] Heger | Des hommes au triangle rose[END_REF].

. Journal intime d'Eugène Wilhelm, Book No. 41, 7 September 1939, f° 110/145.

. Journal intime d'Eugène Wilhelm, Book No.

42, 19-21 December 1939, f°41-43/71. 4 . Howard J. (1999), Men like that: a southern queer history, University of Chicago Press, Chicago, cited byVickers (2010: 65).

. Article 437 of the new Romanian Penal Code introduced the concept of "sexual inversion acts" between men and between women, punishing them with sentences ranging from six months to two years if they created a public scandal. See[START_REF] Carstocea | Repères d'une identité clandestine : considérations historiques sur l'homosexualité en Roumanie[END_REF].

.Tamagne (2006b: 558) describes the case of Dr Anton Purkl, who was retrospectively convicted for acts committed before the annexation.


Mireille Bétermier
email: mireille.betermier@i2bc.paris-saclay.fr

Valérie Borde
email: valerie.borde@curie.fr

Jean-Pierre De Villartay
email: devillartay@gmail.com.

Coupling DNA damage and repair: an essential safeguard during programmed DNA double strand breaks?

Keywords: Programmed DNA double strand break (prDSB), Genome stability, DNA recombination and Repair

DNA double strand breaks (DSBs) are the most toxic DNA lesions given their oncogenic potential. Nevertheless, programmed DSBs (prDSBs) contribute to several biological processes. Formation of prDSBs is the price to pay to achieve these essential biological functions. Generated by domesticated PiggyBac transposases, prDSBs have been integrated in the life cycle of ciliates. Created by Spo11 during meiotic recombination, they constitute a driving force of evolution and ensure balanced chromosome content for successful reproduction. Produced by the RAG1/2 recombinase, they are required for the development of the adaptive immune system in many species. The co-evolution of processes that couple introduction of prDSBs to their accurate repair may constitute an effective safeguard against genomic instability.

Introduction

Living organisms are constantly exposed to genotoxic assaults, which can be of endogenous origin such as cellular respiration or exogenous sources such as radiations or chemical exposures. Several highly conserved DNA repair mechanisms have been selected during evolution to cope with these various damages and maintain genomic integrity. Among DNA lesions, DNA double strand breaks (DSBs) are considered the most toxic and at least two DNA repair pathways (homologous recombination (HR) and non-homologous end joining, or NHEJ) have evolved to cope with DSBs. In addition to repairing pathologic DSBs, these DNA repair pathways are also important for the repair of physiological DSBs or programmed DSBs (prDSBs) created during programmed genome rearrangements (PGR) in ciliates, meiotic recombination for sexual reproduction, and V(D)J recombination. Defects in these processes result in death of progeny (PGR), sterility or aneuploidy (meiotic recombination), and severe immune deficiency (V(D)J recombination). Therefore, the introduction of prDSBs is "the price to pay" for some physiological processes. One can argue that efficient ways to control prDSBs have co-evolved to avoid the deleterious consequences of their mis-repair. Here, we discuss the view that the timely and physical coupling of DNA damage and repair may represent an efficient safeguard during prDSBs.

Coupling DNA damage and NHEJ-mediated repair of prDSBs?

NHEJ is one of the two main DSB repair mechanisms. It operates in all phases of the cell cycle, in contrast to HR, which is excluded from G0/G1. Its catalytic process can be schematically divided into three steps: (i) the heterodimer Ku70/80 identifies and is recruited to the break, prior to the recruitment of the DNA-dependent protein kinase catalytic subunit DNA-PKcs, forming the DNAPK holoenzyme; (ii) If needed, DNA ends are processed ("cleaned") by DNA polymerases, nucleases, and kinases. The processing step is important during V(D)J recombination for the opening of RAG1/2-generated DNA hairpins by the nuclease Artemis; (iii) the DSB is resealed by DNA ligaseIV assisted by the Xlf, MRI and PAXX accessory factors (see [START_REF] Hnizda | Multicomponent assemblies in DNA-double-strand break repair by NHEJ[END_REF] for a recent review on the actors of NHEJ).

Programmed Genome Rearrangement in ciliates: The prototypical example of DNA coupling between DNA damage and repair.

In ciliates, which constitute a monophyletic group of unicellular eukaryotes, the somatic and germline functions of chromosomes are separated into two distinct types of nuclei coexisting in the same cytoplasm [START_REF] Betermier | Programmed Rearrangement in Ciliates: Paramecium[END_REF][START_REF] Yao | Programmed Genome Rearrangements in Tetrahymena[END_REF][START_REF] Yerlici | Programmed Genome Rearrangements in the Ciliate Oxytricha[END_REF]: (i) the diploid micronucleus (MIC), transcriptionally silent during vegetative growth, undergoes meiosis and transmits the parental germline genome to the zygotic nucleus of the following generation; (ii) the polyploid somatic macronucleus (MAC), responsible for gene expression, directs the cell phenotype but is destroyed at each sexual cycle (Figure 1A). Ciliates make their new MAC from a copy of the zygotic nucleus, through a process involving several rounds of whole-genome endoduplication and massive programmed genome rearrangements (PGR) triggered by the introduction of tens of thousands of prDSBs at multiple loci in the genome of the developing new MAC.

During PGR, Paramecium tetraurelia eliminates 25 to 30% of germline DNA from its somatic genome [START_REF] Arnaiz | The Paramecium germline genome provides a niche for intragenic parasitic DNA: evolutionary dynamics of internal eliminated sequences[END_REF][START_REF] Guerin | Flow cytometry sorting of nuclei enables the first global characterization of Paramecium germline DNA and transposable elements[END_REF], including repeated sequences (transposable elements (TEs), minisatellites) and ~45,000 TE-related short and noncoding Internal Eliminated Sequences (IESs), usually found as single-copy elements and scattered all along the ~100-Mbp germline genome. While repeated DNA is eliminated in a heterogeneous manner, IES excision in Paramecium is precise at the nucleotide level. Because IESs interrupt almost half of genes in the germline, their efficient and precise excision ensures that the somatic genome is correctly assembled, a prerequisite for accurate gene expression and progeny survival. DSB repair of excision sites must be efficient and precise in order to preserve the coding capacity of the rearranged somatic genome, especially for intragenic IESs. This precision is likely driven through the pairing of conserved TAs at each 5' overhang, removal of the terminal 5' nucleotide, and addition of one nucleotide at recessed 3' ends [7], ensuring that open reading frames are faithfully reconstituted upon IES excision.

Functional studies of Ku70/Ku80, the earliest-acting NHEJ factors that bind broken DNA ends and protect them against extensive resection, suggest that different solutions to the problem have evolved among ciliate species. P. tetraurelia harbors two almost identical KU70 genes and three more divergent KU80 paralogs, a single of which (KU80c) is specifically expressed during MAC development [12]. In a similar way to Pgm, the development-specific Ku70/Ku80c heterodimer localizes in the new MAC during PGR and expression of KU70 or KU80c is essential for the recovery of a functional somatic genome. Ku80c interacts with Pgm when both proteins are co-expressed in a heterologous system, a property shared by PiggyBac transposases and Ku proteins from other organisms [13]. Strikingly, the depletion of Ku80c abolishes DNA cleavage at IES ends, resulting in retention of all 45,000 IESs genome-wide [12]. In Paramecium, therefore, Ku interaction with Pgm during MAC development is thought to license Pgm-dependent DNA cleavage through a mechanism that remains to be established. Such tight coupling between DSB introduction and repair would ensure that DSBs are introduced only if Ku proteins are present to channel broken ends to the NHEJ pathway (Figure 1B).

In Tetrahymena thermophila, most of the ~12,000 IESs identified in the germline genome lie in non-coding regions [14]. They are also excised by domesticated transposases including a Pgm ortholog (Tpb2, see [15]) and a Pgm-like protein (Lia5, see [16]). Likewise, the C-NHEJ pathway carries out the repair of intergenic IES excision sites but Tpb2 does not require the presence of Ku80 to cleave IES ends [17], suggesting that excision of Tetrahymena intergenic IESs has not imposed the same constraints on the system as compared with excision of Paramecium IESs, the majority of which are intragenic. T. thermophila also harbors 12 intragenic IESs that do not rely on Tpb2 for their elimination.

Remarkably, their excision is extremely precise and carried out by two distinct domesticated PiggyBac transposases, Tpb1 and Tpb6 (Figure 1B), both of which are fused to a Ku80 domain at their N-terminal end [18,[START_REF] Feng | A germline-limited piggyBac transposase gene is required for precise excision in Tetrahymena genome rearrangement[END_REF]. Even though the biological importance of the Ku80 domain still must be tested experimentally, it is tempting to speculate that Ku-transposase fusions have been selected in Tetrahymena to secure the precise excision of intragenic IESs.

In ciliates, Ku80, whether as a separate factor (P. tetraurelia) or linked to the transposase (T. thermophila), appears to play an essential role, independent of its bona fide DNA repair factor function, upstream of the prDSB during PGR.

V(D)J recombination: coupling DNA damage and repair to avoid genomic instability?

V(D)J recombination is the molecular process by which exons encoding the variable domain of immunoglobulins and T cell receptors are assembled prior to their expression, thus ensuring the generation of an almost infinite possibility of antigenic recognition specificities by the adaptive immune system B and T lymphocytes [START_REF] Jung | Mechanism and control of V(D)J recombination at the immunoglobulin heavy chain locus[END_REF]. It is essentially a mechanism related to "cut and paste" transposition, in which previously scattered variable (V), diversity (D), and joining (J) segments are physically associated on the DNA by a combinatorial somatic rearrangement process. V(D)J recombination is initiated by a site specific prDSB introduced by the lymphoid specific, domesticated transposase RAG1 and RAG2 on recombination signal sequences (RSS) that flank all the rearranging V, D, and J segments [START_REF] Schatz | V(D)J recombination: mechanisms of initiation[END_REF][START_REF] Zhang | Transposon molecular domestication and the evolution of the RAG recombinase[END_REF], a catalytic mechanism that evolved from the ancient Transib transposon [START_REF] Liu | Structures of a RAG-like transposase during cut-and-paste transposition[END_REF].

Although V(D)J recombination proceeds through the introduction of the most toxic DNA lesion, it is the "price to pay" for the development of an efficient adaptive immunity, and has been selected for this purpose since the jawless vertebrates [START_REF] Boehm | Origin and evolution of adaptive immunity[END_REF]. Indeed, abortive V(D)J recombination caused by either the inability to introduce the prDSB by RAG1/2 or the inefficiency in processing/repairing these breaks results in the early arrest of B and T cell maturation and the ensuing Severe Combined Immune Deficiency (SCID) both in humans and mice [START_REF] De Villartay | The mechanisms of immune diversification and their disorders[END_REF]. Mouse models also revealed the substantial oncogenic power of V(D)J recombination with the early onset of aggressive pro-B cell lymphomas in mice harboring NHEJ deficiency coupled with TP53 targeted inactivation [START_REF] Ferguson | DNA double strand break repair and chromosomal translocation: lessons from animal models[END_REF]. Likewise, RAG1/2 may have oncogenic mutator functions driving leukemias in humans, such as observed in the context of leukemias harboring the ETV6-RUNX1 chromosomal translocation [START_REF] Papaemmanuil | RAG-mediated recombination is the predominant driver of oncogenic rearrangement in ETV6-RUNX1 acute lymphoblastic leukemia[END_REF].

V(D)J recombination occurs during the G0/G1 phase of the cell cycle, resulting in prDSBs that are repaired through NHEJ [START_REF] Lieber | The mechanism of double-strand DNA break repair by the nonhomologous DNA end-joining pathway[END_REF]. The NHEJ factor Cernunnos was identified through the analysis of immune compromised patients with clinical presentation resembling that of patients with Lig4 syndromes but lacking DNA Ligase IV mutations [START_REF] Buck | Cernunnos, a novel nonhomologous end-joining factor, is mutated in human immunodeficiency with microcephaly[END_REF]. Cernunnos shares sequence homology and interacts with XRCC4 (X4), two features at the basis of its concomitant identification as XRCC4-like factor (Xlf) [START_REF] Ahnesorg | XLF interacts with the XRCC4-DNA ligase IV complex to promote DNA nonhomologous end-joining[END_REF]. XRCC4 and Cernunnos/Xlf interact through their globular head domains, forming long filaments readily visible by electronic microscopy and live imaging [START_REF] Andres | A human XRCC4-XLF complex bridges DNA[END_REF][START_REF] Hammel | XLF regulates filament architecture of the XRCC4.ligase IV complex[END_REF][START_REF] Reid | Organization and dynamics of the nonhomologous endjoining machinery during DNA double-strand break repair[END_REF][START_REF] Ropars | Structural characterization of filaments formed by human Xrcc4-Cernunnos/XLF complex involved in nonhomologous DNA end-joining[END_REF][START_REF] Wu | Non-homologous end-joining partners in a helical dance: structural studies of XLF-XRCC4 interactions[END_REF]. Given this structure, it was proposed that the X4/Xlf filament could form a synapse that would facilitate DNA end tethering for their subsequent ligation by NHEJ.

It was anticipated that because Xlf represents a bona fide NHEJ factor, its deficiency would result in impaired V(D)J recombination. However, V(D)J recombination did not seem to be significantly affected in vivo in the lymphoid lineages either in Xlf-deficient human patients or mouse models [START_REF] Li | Lymphocyte-specific compensation for XLF/cernunnos endjoining functions in V(D)J recombination[END_REF][START_REF] Van Der Burg | Educational paper. The expanding clinical and immunological spectrum of severe combined immunodeficiency[END_REF][START_REF] Vera | Cernunnos deficiency reduces thymocyte life span and alters the T cell repertoire in mice and humans[END_REF]. First, B cell maturation in the bone marrow of Cernunnos patients was not arrested at the pro-B cell stage as expected and found in case of RAG1/2, Artemis, or DNA ligaseIV deficiencies. Second, Xlf KO mouse did not experience severe immune deficiency, only a slight decrease in lymphocyte numbers. Third, Xlf deficiency did not result in V(D)J recombination-driven chromosomal translocation or development of pro-B cell lymphoma when introduced on a TP53 -/-background as observed with all the other models of NHEJxTP53 combined inactivations. Together, it appears that Cernunnos/Xlf is dispensable for V(D)J recombination although its absence clearly results in a major DNA repair defect when it comes to random or accidental DNA lesions such as the ones inflicted by ionizing radiations (IR).

One striking difference between IR-and V(D)J-driven DSBs is the presence of RAG1/2 in the latter. The RAG1/2 complex is known to remain on the DSB it has initiated as the post cleavage complex (PCC) [START_REF] Schatz | V(D)J recombination: mechanisms of initiation[END_REF], providing a possible means to tether DNA ends, which would be redundant to the expected function of the X4/Xlf filament (Figure 2A). Under this hypothesis, the sole presence of the PCC would provide a DNA repair synapse complementing the absence of the X4/Xlf filament during V(D)J recombination while such synapse would be missing at genotoxic-driven DSBs. The stability of the PCC relies on the C terminus region of RAG2, a region outside of the core and not essential for V(D)J recombination, as shown in vitro and in vivo in the RAG2 cc mouse model specifically engineered to restrict RAG2 to its core domain [START_REF] Deriano | The RAG2 C terminus suppresses genomic instability and lymphomagenesis[END_REF][START_REF] Liang | The "dispensable" portion of RAG2 is necessary for efficient V-to-DJ rearrangement during B and T cell development[END_REF]. V(D)J recombination is not grossly affected in RAG2 cc or Xlf -/-single mutant conditions, but is fully abrogated in RAG2 cc xXlf -/- mice, resulting in SCID animals devoid of mature B and T lymphocytes [START_REF] Lescale | RAG2 and XLF/Cernunnos interplay reveals a novel role for the RAG complex in DNA repair[END_REF]. Based on these observations a 2-synapse model (Fig. 2A) was proposed in which the PCC complex on one hand and the X4/Xlf filament on the other hand help maintain genome integrity during V(D)J recombination. A similar functional redundancy operating specifically during V(D)J recombination was observed between Xlf and ATM or H2AX [START_REF] Zha | ATM damage response and XLF repair factor are functionally redundant in joining DNA breaks[END_REF], and 53BP1 [START_REF] Oksenych | Functional redundancy between repair factor XLF and damage response mediator 53BP1 in V(D)J recombination and DNA repair[END_REF][START_REF] Liu | Overlapping functions between XLF repair protein and 53BP1 DNA damage response factor in end joining and lymphocyte development[END_REF] as well as between Xlf and the recently described NHEJ factors PAXX [START_REF] Abramowski | PAXX and Xlf interplay revealed by impaired CNS development and immunodeficiency of double KO mice[END_REF][START_REF] Balmus | Synthetic lethality between PAXX and XLF in mammalian development[END_REF][START_REF] Hung | Deficiency of XLF and PAXX prevents DNA double-strand break repair by non-homologous end joining in lymphocytes[END_REF][START_REF] Kumar | PAXX and XLF DNA repair factors are functionally redundant in joining DNA breaks in a G1-arrested progenitor B-cell line[END_REF][START_REF] Lescale | Specific Roles of XRCC4 Paralogs PAXX and XLF during V(D)J Recombination[END_REF][START_REF] Liu | PAXX promotes KU accumulation at DNA breaks and is essential for end-joining in XLF-deficient mice[END_REF] or MRI [START_REF] Hung | MRI Is a DNA Damage Response Adaptor during Classical Non-homologous End Joining[END_REF] thus establishing a "synthetic dysfunction" among these factors (Fig. 2B). RAG2 cc and ATM or PAXX combined deficiencies do not result in impaired V(D)J recombination, suggesting that these three factors are epistatic, opposite to that of Xlf (Figure 2B) [START_REF] Lescale | RAG2 and XLF/Cernunnos interplay reveals a novel role for the RAG complex in DNA repair[END_REF][START_REF] Lescale | Specific Roles of XRCC4 Paralogs PAXX and XLF during V(D)J Recombination[END_REF]. It will be interesting to better understand the status of XRCC4 in this two-tier mechanism given its physical interaction with Xlf. However, XRCC4 KO mice are embryonic lethal and demonstrate impaired V(D)J recombination in fetuses because XRCC4 is required for DNAligase IV stability [START_REF] Frank | DNA ligase IV deficiency in mice leads to defective neurogenesis and embryonic lethality via the p53 pathway[END_REF][START_REF] Gao | Interplay of p53 and DNA-repair protein XRCC4 in tumorigenesis, genomic stability and development[END_REF]. Hence, XRCC4 KO phenocopies DNA-Lig4 KO condition. In contrast, the absence of immune deficiency in human primordial dwarfism with microcephaly syndrome caused by hypomorphic (yet severe) XRCC4 mutations suggests that, like Xlf, XRCC4 is not required for V(D)J recombination [START_REF] De Villartay | When natural mutants do not fit our expectations: the intriguing case of patients with XRCC4 mutations revealed by whole-exome sequencing[END_REF].

The demonstration of these functional interplays between RAG2, Xlf, and other DNA repair factors during V(D)J recombination suggests the possible existence of a "coupling" of DNA damage and repair during V(D)J recombination like the one described during PGR in ciliates. The challenge is now to fully understand how functional links between the RAG1/2 complex and the DNA repair apparatus translate into physical interaction of key components.

Interestingly with regard to the analogy with PGR in ciliates, Raval et al. reported on the interaction of RAG1 with the Ku70/Ku80 complex [START_REF] Raval | Evidence for Ku70/Ku80 association with full-length RAG1[END_REF]. Moreover, an interaction between RAG1 and another critical DNA repair factor, MDC1, was also reported [START_REF] Coster | A dual interaction between the DNA damage response protein MDC1 and the RAG1 subunit of the V(D)J recombinase[END_REF]. The existence of a physical link between RAG1/2 and the DNA repair machinery certainly accredits the hypothesis of a DNA damage-repair coupling during V(D)J recombination.

Meiotic recombination: Homologous Recombination is also concerned

As opposed to NHEJ, homologous recombination uses DNA sequence homology on an intact DNA template to repair the broken DNA molecule after a DSB. The repair template can be located on the sister chromatid, on a homologous chromosome, or elsewhere in the genome. The first step of homologous recombination is the resection of the 5' ends of the DSB, first by the MRE11 complex, then by EXO1 and BLM/DNA2, which generates protruding 3' ends that invade the repair DNA template, through the action of a RecA-related recombinase, such as Rad51 [START_REF] Kowalczykowski | An Overview of the Molecular Mechanisms of Recombinational DNA Repair[END_REF]. In somatic cells, the preferred DNA repair template is the sister chromatid and therefore, homologous recombination is restricted to the G2/M phases of the cell cycle. During the meiotic prophase of sexually reproducing organisms, the topoisomerase-like protein Spo11 initiates meiotic recombination by introducing hundreds of prDSBs along chromosomes. These prDSBs are important for recognition and pairing of homologs and a few of them will be repaired by crossovers, generating a physical link between homologs essential for their accurate segregation into the future gametes [58].

Meiotic recombination is a risky business for genome integrity of germ cells. Indeed, the burden of prDSBs that are introduced by Spo11 during meiotic recombination is at high risk of generating unwanted translocations or chromosome rearrangements, and their formation is therefore highly controlled by the use of several processes specific to meiotic cells. First, the DSB formation and repair steps both take place in a specific chromosome compartment, the chromosome axis, from which chromatin loops emanate, and which will be the place where the homologs become fully aligned within the synaptonemal complex (Figure 3). The DNA sequences that are cleaved by Spo11 are preferentially located on the chromatin loops, although these sequences interact with proteins present along the chromosome axis, implying a spatial folding of the loop towards the chromosome axis during recombination. Spo11-accessory proteins link double-strand break sites to the chromosome axis in early meiotic recombination [59]. This allows both to easily control the number of prDSBs generated, and also to physically "isolate" the cleaved DNA sequence from nonallelic/non-homologous sequences. This physical tethering of the sequence to be cleaved onto the chromosome axis is facilitated by a specific histone modification, H3K4me3, which bridges the DSB sequences to the DSB proteins located on the chromosome axis [START_REF] Borde | Programmed induction of DNA double strand breaks during meiosis: setting up communication between DNA and the chromosome structure[END_REF] thus ensuring that meiotic prDSBs are formed within the correct spatial context. Another regulation is exerted at the level of the "DSB forming complex". Indeed, in all organisms studied, the catalytic subunit Spo11 alone is not sufficient for DSB formation to take place, and multiple other proteins (9 in budding yeast, at least 5 in mammals) are required [START_REF] Lam | Mechanism and regulation of meiotic recombination initiation[END_REF][62][START_REF] Stanzione | Meiotic DNA break formation requires the unsynapsed chromosome axis-binding protein IHO1 (CCDC36) in mice[END_REF].

Mainly discovered in budding yeast, these proteins now appear conserved among many organisms, although they lack clear sequence homology, which renders them difficult to identify. These proteins form several proposed subcomplexes that interact together to promote DSB formation: a "core complex" composed of Spo11 (homolog of the catalytic TopoVI-A subunit) and a homolog of the TopoVI-B subunit [START_REF] Robert | The TopoVIB-Like protein family is required for meiotic DNA double-strand break formation[END_REF][START_REF] Vrielynck | A DNA topoisomerase VI-like complex initiates meiotic recombination[END_REF], a "RMM" complex proposed to interact directly with the chromosome axis, and other components that can vary depending on the species [START_REF] Lam | Mechanism and regulation of meiotic recombination initiation[END_REF]. Among the Spo11 protein partners required for DSB formation or localization, several are also important for DSB repair: the Mre11 complex (in budding yeast, the worm C. elegans, and maybe in mammals), Narya in the fruit fly Drosophila, and PRDM9, which, is essential for their targeting to specific DNA sequences in humans and mice, despite not being essential for DSB formation.

The MRE11 complex

The MRE11 complex is well known for the signaling and processing of DSBs [START_REF] Oh | Role of the Mre11 Complex in Preserving Genome Integrity[END_REF]. Its endonuclease activity is required to process meiotic DSBs, by removing the Spo11 protein together with a short oligonucleotide from DSB ends [67]. In addition, at least in the budding yeast S. cerevisiae and in the nematode C. elegans, this complex is integrated in the process that is required for prDSB formation by Spo11 [START_REF] Chin | C. elegans mre-11 is required for meiotic recombination and DNA repair but is dispensable for the meiotic G(2) DNA damage checkpoint[END_REF][START_REF] Usui | A DNA damage response pathway controlled by Tel1 and the Mre11 complex[END_REF]. The functions of the MRE11 complex in DSB formation and repair are genetically separable, and its function for DSB formation seems to involve mainly the Mre11 and Rad50 subunits [START_REF] Girard | Interdependent and separable functions of Caenorhabditis elegans MRN-C complex members couple formation and repair of meiotic DSBs[END_REF][START_REF] Oh | Xrs2 Dependent and Independent Functions of the Mre11-Rad50 Complex[END_REF]. In mammals, whether the MRE11 complex is needed for Spo11-induced DSB formation is not clear at the moment, because members of the MRE11 complex are essential for viability, so only hypomorphic mutants of the MRE11 complex could be tested in the mouse for their effect on fertility, and they showed only defects in meiotic DSB repair [START_REF] Cherry | The Mre11 complex influences DNA repair, synapsis, and crossing over in murine meiosis[END_REF]. Conditional knock out of the Mre11 complex specifically in meiotic cells would be required to know if it is also required for meiotic DSB formation in mammals. In budding yeast, components of the MRE11 complex appear to directly interact with other DSB formation proteins [START_REF] Arora | Antiviral protein Ski8 is a direct partner of Spo11 in meiotic DNA break formation, independent of its cytoplasmic role in RNA metabolism[END_REF], implying a specialization of the MRE11 complex for the immediate signaling and processing of these programmed meiotic DSBs. Likewise, in the plant Arabidopsis thaliana, although not strictly required for meiotic DSB formation, a member of the MRE11 complex directly interacts with a protein required for DSB formation ( [START_REF] Waterworth | Arabidopsis TAF1 is an MRE11-interacting protein required for resistance to genotoxic stress and viability of the male gametophyte[END_REF] and Mathilde Grelon, personal communication). It is attractive to propose that incorporating the signaling and repair Mre11 complex in the step of meiotic DSB formation allows the immediate processing of meiotic DSBs into the homologous recombination pathway.

Narya

Another example of coupling between meiotic DSB formation and repair comes from the fruit fly Drosophila, where a protein, Narya, fulfills functions both for formation and repair of meiotic DSBs with a crossing over, to ensure proper homolog segregation and successful meiosis [START_REF] Lake | Narya, a RING finger domain-containing protein, is required for meiotic DNA double-strand break formation and crossover maturation in Drosophila melanogaster[END_REF]. Narya is a RING finger protein that is redundant with another related protein, Nanya, for meiotic DSB formation and repair. It also interacts with Vilya, a third protein of the family, required for DSB formation and interacting with MEI22, one of the Drosophila DSB proteins [76]. Interestingly, a separation-of-function allele of Narya, in its RING finger domain, shows that Narya is not only involved in DSB formation, but also required for their repair as a crossover. In addition, the three proteins show two sequential localization patterns; first, early with DSB sites and then, to crossover sites [START_REF] Lake | Narya, a RING finger domain-containing protein, is required for meiotic DNA double-strand break formation and crossover maturation in Drosophila melanogaster[END_REF]76]. This illustrates again a double function for meiotic DSB formation and their repair into crossovers within a single protein, therefore directly coupling these two steps of meiotic recombination.

PRDM9

The histone methyltransferase PRDM9, responsible for targeting meiotic prDSBs to its consensus DNA binding sequence in many organisms including mice and humans, is also critical for meiotic prDSB repair. In its absence, Spo11 forms meiotic prDSBs at "default" chromatin accessible locations within functional genomic elements, which are not well repaired for unclear reasons [77,[START_REF] Grey | PRDM9, a driver of the genetic map[END_REF]. In addition, if PRDM9 is present on only one homolog owing to a polymorphism affecting its consensus binding sequence, this also creates problems in DSB repair [79]. This suggests that the symmetric binding of PRDM9 to both homologs, thanks to its sequence specificity, facilitates the repair, perhaps by bringing close together into the chromosome axis the two chromatid sequences that will experience the recombination event (Figure 3). In favor of this hypothesis, PRDM9 physically interacts with several components of the chromosome axis [START_REF] Parvanov | PRDM9 interactions with other proteins provide a link between recombination hotspots and the chromosomal axis in meiosis[END_REF]. PRDM9 therefore represents yet another example of coupling prDSB formation and repair within a single protein during programmed meiotic recombination.

Concluding remarks

Besides meiosis, PGR, and V(D)J recombination, prDSBs have been identified during signal-induced transcription in several experimental settings (see [START_REF] Puc | Physiological functions of programmed DNA breaks in signalinduced transcription[END_REF] for a recent review).

These activity-induced prDSBs occur primarily in early response genes and are introduced by the topoisomerase IIb. This is in particular the case in the response of MCF-7 cells to estradiol [START_REF] Ju | A topoisomerase IIbeta-mediated dsDNA break required for regulated transcription[END_REF] or activation through glucocorticoid receptors [START_REF] Trotter | Glucocorticoid Receptor Transcriptional Activation via the BRG1-Dependent Recruitment of TOP2beta and Ku70/86[END_REF]. prDSBs also occur in vivo and in vitro upon neuronal activity [START_REF] Madabhushi | Activity-Induced DNA Breaks Govern the Expression of Neuronal Early-Response Genes[END_REF]85]. Interestingly, in the case of the glucocorticoid receptor-induced transcriptional activation, recruitment of Top2b and Ku70/86 via the BRG1 transcription activator-containing chromatin-remodeling complex is required at GRresponsive promoters [START_REF] Trotter | Glucocorticoid Receptor Transcriptional Activation via the BRG1-Dependent Recruitment of TOP2beta and Ku70/86[END_REF]. This suggests that a subset of DNA repair factors may be in place before prDSBs, thus accrediting the hypothesis of a possible coupling of DNA damage and repair during signal-induced transcription. Finally, beside Pgm in ciliates and RAG1/2, two other domesticated transposases have been identified in human cells, the piggyBac transposable element-derived 5 (PGBD5) [86] and THAP9, related to the Drosophila Pelement transposase [87], the exact functions of which are presently unknown. The deregulated expression of PGBD5 in rhabdoid tumors in children participates in the oncogenic transformation by promoting site-specific DNA rearrangements within tumor suppressor genes [88]. Whether this deleterious activity of PGBD5 is counteracted in its physiological context by a mechanism related to DNA damage-repair coupling is of course speculative but represents an interesting issue to follow. If this were to be true, it would reinforce the idea that DNA damage-repair coupling may represent an essential step in the transposase domestication process.

Altogether coupling DNA damage and repair may have co-evolved with prDSBs to ensure their efficient repair and thus avoid any associated genomic instability. Several

Highlights

• Several biological processes (meiosis, V(D)J recombination, PGR in ciliates, signalinduced transcription) proceed via introduction of programmed DSBs (prDSBs).

• DSBs being the most toxic DNA lesions, as potentially oncogenic, prDSBs are likely associated with very efficient, multi-layered DNA repair mechanisms. Coupling DNA damage and repair is one critical layer.

• Ku80 is a critical factor to link DNA damage and repair during PGR in ciliates

• The C terminus of RAG2 may be responsible for the DNA damage-repair coupling during V(D)J recombination as a safeguard against genome instability.

• During meiotic recombination, a specific pathway ensures that meiotic DSBs are formed within the correct spatial chromosomal context.

• The MRE11 complex is required for the formation of prDSBs by Spo11 during meiotic recombination.

• DNA damage-repair coupling may represent an essential step in the domestication process of PiggyMac, RAG1/2 and other transposases.

Outstanding Questions Box

• What are the exact mechanisms and critical players of DNA damage-repair coupling during prDSBs?

• What are the downstream consequences of uncoupling DNA damage-repair during prDSBs driven processes (for example: genetic instability and tumor development, cellular degeneracy)?

• Is DNA damage-repair coupling a general rule that applies to all biological processes that proceed through prDSBs?

Glossary

• DSBs: DNA double strand breaks can be "accidental" as a result of environment insult or "programmed" (prDSBs) as part of essential physiological processes (meiosis, V(D)J recombination, PGR in ciliates).

• HR: The Homologous Recombination DNA repair pathway is one of the two main mechanisms, with NHEJ, to repair DSBs. It operates exclusively in S phase of the cell cycle when a sister chromatid is available as template. • SCID: Severe Combined Immune Deficiency is a rare condition in humans (and engineered mouse models) characterized by a profound defect in the development/function of the adaptive immune system. Impaired V(D)J recombination results in SCID.

• Spo11: Catalytic subunit of a topoisomerase-like complex that introduces prDSBs during meiosis • V(D)J Recombination: Lymphoid-specific somatic DNA rearrangement process of immunoglobulin and T cell receptor (TCR) genes initiated by the RAG1/2 factors aimed at generating the antigenic diversity (repertoire) of the adaptive immune system. During meiosis, homologous chromosomes experience homologous recombination, which promotes their pairing, crossover and physical attachment through the chiasmata.

Chromosomes are organized around a protein axis (blue and red lines for maternal and paternal chromosomes), from which chromatin loops emanate (gray). DSBs (yellow lightening) are formed to initiate recombination, which culminates into at least one crossover pair of homologs. Programmed DSBs occur at hotspot sequences, which become transiently tethered to the chromosome axis where DSB proteins (including the catalytic subunit Spo11) are located. Among these, the Mre11 complex is necessary both for the formation of DSBs by Spo11 and for their repair, highlighting the specialized coupling between DSB formation and repair during meiosis. Other examples of such coupling are discussed in the text.

Paramecium

  IESs are flanked by conserved TA dinucleotides. IES excision is initiated by 4-base staggered double-strand DNA cleavages centered on each flanking TA [7]. The endonuclease responsible for prDSB introduction at IES ends is a domesticated transposase called PiggyMac (Pgm), whose conserved DDD catalytic triad, characteristic of transposases from the PiggyBac family, is essential for its function [8, 9]. Pgm is expressed during MAC development and localizes specifically in the developing new MAC by the time DNA elimination takes place. Five groups of Pgm-like domesticated PiggyBac transposases (PgmL1 to PgmL5) assist Pgm in cleaving DNA [10]. Each PgmL can interact individually with Pgm and is essential for IES excision genome-wide. None of them harbors a fully conserved catalytic site, suggesting that they play an architectural role during assembly of the IES excision complex, with PgmL1 and PgmL3 fine-tuning the precise positioning of DNA cleavage at IES boundaries. Once introduced, chromosomal prDSBs are repaired by the Ligase IV-and Xrcc4-dependent classical NHEJ pathway (C-NHEJ) [11]. NHEJ-mediated

4 87

 4 questions remain to be addressed: (i) what are the exact mechanisms governing this coupling, (ii) given the oncogenic power of DSBs, what would be the consequences of losing this coupling (see Outstanding Questions)? 7 Gratias, A. and Bétermier, M. (2003) Processing of double-strand breaks is involved in the precise excision of Paramecium IESs. Mol. Cell. Biol. 23, 7152-7162 8 Baudry, C., et al. (2009) PiggyMac, a domesticated piggyBac transposase involved in programmed genome rearrangements in the ciliate Paramecium tetraurelia. Genes & development 23, 2478-2483 9 Dubois, E., et al. (2017) Multimerization properties of PiggyMac, a domesticated piggyBac transposase involved in programmed genome rearrangements. Nucleic Acids Res 45, 3204-3216 10 Bischerour, J., et al. (2018) Six domesticated PiggyBac transposases together carry out programmed DNA elimination in Paramecium. Elife 7 11 Kapusta, A., et al. (2011) Highly precise and developmentally programmed genome assembly in Paramecium requires ligase IV-dependent end joining. PLoS Genet 7, e1002049 12 Marmignon, A., et al. (2014) Ku-mediated coupling of DNA cleavage and repair during programmed genome rearrangements in the ciliate Paramecium tetraurelia. PLoS genetics 10, e1004552 13 Jin, Y., et al. (2017) DNA-PK facilitates piggyBac transposition by promoting pairedend complex formation. Proc Natl Acad Sci U S A 114, 7408-7413 14 Hamilton, E.P., et al. (2016) Structure of the germline genome of Tetrahymena thermophila and relationship to the massively rearranged somatic genome. Elife 5 15 Cheng, C.Y., et al. (2010) A domesticated piggyBac transposase plays key roles in heterochromatin dynamics and DNA cleavage during programmed DNA deletion in Tetrahymena thermophila. Molecular biology of the cell 21, 1753-1762 16 Shieh, A.W. and Chalker, D.L. (2013) LIA5 is required for nuclear reorganization and programmed DNA rearrangements occurring during Tetrahymena macronuclear differentiation. PLoS One 8, e75337 17 Lin, I.T., et al. (2012) An essential role for the DNA breakage-repair protein Ku80 in programmed DNA rearrangements in Tetrahymena thermophila. Molecular biology of the cell 23, 2213-2225 18 Cheng, C.Y., et al. (2016) The piggyBac transposon-derived genes TPB1 and TPB6 mediate essential transposon-like excision during the developmental rearrangement of key genes in Tetrahymena thermophila. Genes & development 30, 2724-2736 85 Suberbielle, E., et al. (2013) Physiologic brain activity causes DNA double-strand breaks in neurons, with exacerbation by amyloid-beta. Nature neuroscience 16, 613-621 86 Henssen, A.G., et al. (2015) Genomic DNA transposition induced by human PGBD5. eLife Majumdar, S., et al. (2013) The human THAP9 gene encodes an active P-element DNA transposase. Science 339, 446-448 88 Henssen, A.G., et al. (2017) PGBD5 promotes site-specific oncogenic mutations in human tumors. Nature genetics 49, 1005-1014

•

  Meiosis: Meiosis is the process of chromosome segregation during the formation of gametes. prDSBs are introduced by Spo11 during meiosis • MRE11 complex: Composed of meiotic recombination 11 (MRE11), RAD50 and Nijmegen breakage syndrome 1 (NBS1 or Nibrin, Xrs2 in budding yeast). Acts in the sensing and signaling of DSBs. The endonuclease activity of MRE11 is essential for the processing of protein-linked meiotic DSBs. • NHEJ: The Non Homologous End Joining DNA repair pathway is one of the two main mechanisms, with HR, to repair DSBs. It operates in all phases of the cell cycle. • PGR: Programmed Genome Rearrangement that reproducibly eliminates large fractions of germline DNA (25 to 95% according to species) during formation of the Macronucleus (MAC) during the ciliate sexual cycle • PiggyMac (Pgm): Domesticated transposase responsible for PGR in the ciliate Paramecium. • RAG1 & RAG2: The Recombination Activating Gene 1 & 2 constitute the domesticated transposase initiating V(D)J recombination in immature B and T lymphocytes.

Figure 1 :

 1 Figure 1: Coupling between DSB formation and repair during programmed genome rearrangements in ciliates A) In the ciliate Paramecium tetraurelia, vegetative cells harbor two MICs (black) and one MAC (gray). During sexual reproduction, MICs undergo meiosis, a single meiotic product divides and yields two gametic nuclei (black), while all others are degraded (light gray). During conjugation, following reciprocal exchange of gametic nuclei between mating partners, the resident and incoming nuclei fuse to give a diploid zygotic nucleus (black); during autogamy (a self-fertilization process), the zygotic nucleus results from the fusion of both gametic nuclei from the same cell. The zygotic nucleus then divides twice: two of the resulting nuclei become the new MICs (black) and the other two differentiate into new MACs (hatched purple and blue). Programmed DNA elimination takes place during MAC development. Following mitosis of the new MICs, the new MACs segregate into each daughter cell. Throughout the whole process, the old MAC is fragmented and is eventually lost after a few cell divisions. B) In Paramecium, the presence of Ku is required for Pgm to cleave DNA at IES ends, indicative of tight coupling between DSB formation and repair.Tetrahymena intragenic IESs are excised by domesticated transposases (Tpb1 and Tpb6) fused to a Ku80-like domain, the functional importance of which has not been established.

Figure 2 :

 2 Figure 2: Coupling between DSB formation and repair during V(D)J Recombination? A) Two complementary synapses (the XLF/XRCC4 filament and the RAG1/2 post cleavage complex) ensure DNA end tethering during V(D)J recombination. The loss of both synapses results in major genomic instability with the development of lymphomas. B) Synthetic dysfunction of V(D)J recombination highlights two complementary axes during the repair phase of V(D)J recombination. RAG2 participates in the ATM-PAXX-MRI axis, complementary to the XLF-XRCC4 axis.

Figure 3 :

 3 Figure 3: Coupling between DSB formation and repair during programmed meiotic recombination.

Acknowledgments

We thank Mathilde Grelon (INRA, Versailles) for personal communication. Work in our respective laboratories is supported by institutional grants from INSERM, CNRS, ANR ("Investissements d'avenir" program ANR-10-IAHU-01; ANR-13-PRTS-0004; ANR-18-CE12-0018; ANR-14-CE10-0005-01; and ANR-18-CE12-0005-02), INCa (PLBIO16-280), and grants from Ligue Nationale Contre le Cancer (Equipe Labellisée), Fondation pour la Recherche Médicale (Equipe FRM EQU201903007785) and AT-Europe Fundation.


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