Les origines de réplication sont les sites à travers le génome où est initiée la synthèse de l’ADN. Les multiples cartographies des origines de réplication dans des cellules de vertébrés ont identifié une association entre origines de réplication et motifs G4. Les motifs G4 sont des séquences ayant le potentiel de se replier en G-quadruplexe. Des travaux menés précédemment au laboratoire ont montré que la capacité d’un motif G4 à se replier en G-quadruplexe est essentielle pour l’activité de deux origines de réplication modèles dans la lignée cellulaire de poulet DT40. Cependant, le motif G4 n’est pas suffisant pour spécifier une origine de réplication. Dans l’origine modèle βA, un élément cis de 227 pben 3’ du motif G4 est également nécessaire pour l’initiation de la réplication. L’analyse de la séquence de cet élément indique qu’il comporte plusieurs motifs connus pour être des sites de fixation de facteurs de transcription. Nous avons testé le rôle potentiel de ces motifs en évaluant l’effet de leurs délétions individuelles sur l’activité de l’origine βA. Ces travaux ont identifié les boites TATA et CCAAT, pouvant être liées par le facteur TBP (TATA Binding Protein) et NFY (Nuclear Factor Y) respectivement, comme étant les éléments cruciaux avec le motif G4 pour l’initiation de la réplication. Nous avons cherché à éclaircir de quelle manière ces éléments permettent la spécification d’une origine de réplication. A cet effet, nous avons émis l’hypothèse selon laquelle les motifs G4 qui se trouvent au niveau des origines de réplication sont ceux qui in vivo sont capables de former un G-quadruplexe. La formation du G-quadruplex dans l’origine βA dépendrait alors de la présence des boites TATA et CCAAT qui peuvent recruter des facteurs de transcription favorisant l’ouverture de la double hélice de l’ADN et le repliement du G-quadruplex. Cette hypothèse prévoit que la stabilisation d’un G-quadruplexe in vivo est nécessaire et suffisante pour former une nouvelle origine de réplication. Nous avons donc testé cette hypothèse de deux manières. D’abord, nous avons entrepris de stabiliser un G-quadruplex à une position donnée du génome en induisant la transcription d’un motif G4. Ensuite, nous avons déterminé les effets d’une stabilisation globale des G-quadruplexes à travers le génome sur la position des origines de réplication. Pour cela, nous avons cartographié les origines de réplication dans des lignées de cellules DT40 dans lesquelles des facteurs impliqués dans la linéarisation des G-quadruplexes ont été inactivés. Selon notre hypothèse, en l’absence de tels facteurs, comme l’hélicase FancJ ou l’ADN polymérase translésionnelle Rev1, davantage de motifs G4 pourraient se replier et former une origine de réplication. Les résultats obtenus avec chacune des deux approches indiquent que la stabilisation de G-quadruplexes ne permet pas de produire de nouvelles origines de réplication. L’ensemble de nos données indique que l’activité de l’origine βA dépend d’un motif G4 et des boites TATA et CCAAT. La manière par laquelle l’ensemble de ces éléments permettent l’initiation de la réplication reste à éclaircir / Replication origins are the position where DNA synthesis is initiated. Mapping of replication origins across the genome showed a link between origins and G4 motifs. G4 motifs are sequences the potential for forming G-quadruplexes. Works carried out previously in the laboratory showed that the ability to fold into G-quadruplex is critical for the activity of two model origin in the DT40 cell line. However, the G4 motif is not enough to specify a replication origin. In the βA model origin, a 227 bp cis element is required for the initiation of replication. The analysis of this sequence indicates the presence of several motifs known to be binding sites for transcription factors. We tested the potential roles of these motifs by evaluating the effect of their individual deletion on the activity of the βA origin. This work identified the TATA and CCAAT boxes who bind TBP (TATA Binding Protein) and NFY (Nuclear Factor Y) respectively as the crucial elements, with the G4 motifs, pour the initiation of replication.We endeavored to shed light on the manner by which these elements enable the specification of a replication origin. We hypothesized that the G4 motifs associated with replication origins are those able to form a G-quadruplex in vivo. The formation of the G-quadruplex of the βA origin would require the presence of the TATA and CCAAT boxes who could recruit transcription factors facilitating the opening of the double helix and G-quadruplex folding. We tested this hypothesis by two different manners. First, we undertook to stabilize a G-quadruplex at a given position in the genome by inducing the transcription of a G4 motif. Then, we observed the effects of a genome wide stabilization of G-quadruplexes on the position of replication origins. For that, we mapped replication origins in DT40 cell lines in which factors implicated in G-quadruplex linearization are inactivated. According to our hypothesis, without such factors, like the FancJ helicase of the translesional DNA polymerase Rev1, more G4 motifs could fold into G-quaduplexes and specify replication origins

RNF4 belongs to the family of SUMO-targeted ubiquitin E3 ligases (STUbLs). The role of STUbLs in maintaining genomic stability was first discovered in yeast. Theyeast STUbL mutants displayed genomic instability, elevated mutation rates, sensitivity to DNA damaging agents and also demonstrated synthetic lethality with other DNA repair genes. Although the role of vertebrate RNF4 in the DNA damage response was not yet established, it could rescue the Schizosaccaromyces pombe STUbL mutant phenotypes, showing that RNF4 is a functional homologue of the yeast STUbL proteins,and that it might be implicated in the vertebrate DNA damage response.A homozygous knockout of RNF4 in the DT40 chicken lymphocyte cell line was generated to investigate the involvement of vertebrate RNF4 in protecting cells against DNA damage. Although the complete loss of RNF4 did not affect cell proliferation or cell cycle distribution, the RNF4 -/- cells exhibited a selective hypersensitivity to some S-phase specific DNA damaging agents. This hypersensitivity could be rescued by introducing an ortholog of RNF4 from another vertebrate species, and this was dependent on a functional ubiquitin E3 ligase activity of RNF4.To explore the physiological function of RNF4 in the context of a wholeorganism, Danio rerio was chosen as an in vivo model. Danio rerio RNF4 sharedsimilar in vitro biochemical characteristics as RNF4 from other vertebrates – it was able to autoubiquitylate itself and also ubiquitylate SUMO2 chains. In Danio rerio, RNF4 is a maternally provided gene and is highly expressed in the adult gonads. In the ovaries, RNF4 expression was restricted to the early stage oocytes, suggesting a possible role in oocyte development. Loss-of-function studies in Danio rerio were performed using morpholino knockdown and zinc-finger knockout technologies, and the depletion of RNF4 in zebrafish did not affect early embryonic development or viability of the animal.The results presented in this thesis suggests that while vertebrate RNF4 is notlikely to be an essential gene in some vertebrates, it plays a role in the DNA damage response and might be implicated in gonad development in Danio rerio. The zinc-finger knockout model has just been established and a more in-depth analysis is necessary to shed more light on the in vivo functions of RNF4.

Kazunori Yoshikiyo, Katja Kratz, Kouji Hirota, Kana Nishihara, Minoru Takata, Hitoshi Kurumizaka, Satoshi Horimoto, Shunichi Takeda, and Josef Jiricny "KIAA1018/FAN1 nuclease protects cells against genomic instability induced by interstrand cross-linking agents" PNAS 2010 107 (50) 21553-21557; published ahead of print November 29, 2010, doi:10.1073/pnas.1011081107 / 京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第12772号 / 論医博第2063号 / 新制||医||1000(附属図書館) / 30755 / (主査)教授 小松 賢志, 教授 小川 誠司, 教授 松本 智裕 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18144号 / 医博第3864号 / 新制||医||1002(附属図書館) / 31002 / 京都大学大学院医学研究科医学専攻 / (主査)教授 松原 和夫, 教授 髙橋 淳, 教授 福山 秀直 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DGAM

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Mutagenesis following peer review. The definitive publisher-authenticated version is available online at:http://mutage.oxfordjournals.org/content/early/2015/08/03/mutage.gev055.full. / 京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19588号 / 医博第4095号 / 新制||医||1014(附属図書館) / 32624 / 京都大学大学院医学研究科医学専攻 / (主査)教授 小泉 昭夫, 教授 渡邊 直樹, 教授 高田 穣 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

In the present investigation, microarray analysis was used to identify potential TCDD gene targets. Three microarray experiments were performed to study the effect of TCDD in an established chicken B-cell line (DT40), in a chicken macrophage cell line (HD11), and in the bursa of Fabricius from embryos exposed in ovo at 6 days of incubation. From the DT40 microarray analyses, clones with sequence similarity to the apoptotic genes caspase 8 and caspase 9, and the transcription factor NFΜB, among others, were identified. Real-time quantitative polymerase chain reaction (RT-PCR) revealed that TCDD elicits aryl hydrocarbon receptor (AhR)-mediated apoptosis in the avian DT40 pre-B-cell line through activation of caspases 9 and 3 (see chapter III). During the course of the HD11 microarray analyses, a consistent down-regulation of the matrix metalloprotease MMP-2 was observed. This finding was the basis for the hypothesis that TCDD has an effect on the gene expression of the MMP-2 and MMP-9 in macrophages. Then, gene expression analysis and functional zymography showed that TCDD impairs the MMP-2 and MMP-9 response to LPS stimulation in HD11 chicken macrophages (see chapter V). The microarray analyses of the embryonic bursa of Fabricius provided the basis to further study of the effect of TCDD in the chicken embryo. The shifted genes were classified according to their function. The down-regulated genes included: precursor of matrix metalloprotease-inhibitor, histone acyl-transferase 1, homeobox protein CUX-2, Death Associated Protein Kinase, and UDPglucosyl transferase, among others. The up-regulated genes included: phosphoinositidespecific phospholipase, acyl Co-A oxidase, and protein effector of Cdc42, among others. Together, these microarray analyses produced a database of genes of interest that will provide sufficient hypotheses to inspire multiple investigations aimed at confirming and refining the gene expression alterations as a consequence of TCDD exposure.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19555号 / 医博第4062号 / 新制||医||1012(附属図書館) / 32591 / 京都大学大学院医学研究科医学専攻 / (主査)教授 高田 穣, 教授 戸井 雅和, 教授 鈴木 実 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM