Résumé
The genetic material can suffer a variety of damages that can be caused by endogenous and exogenous damaging agents. Lesions on one of the DNA strand are repaired by mismatch repair, nucleotide or base excision repair or bypassed by translesion synthesis. DNA double strand break are mainly repaired by Non Homologous End Joining and homologous recombination. Recent studies have shown that some Melanoma Antigen-encoding (MAGE) proteins are involved in DNA damage repair. Those proteins are part of a family of more than 50 genes in Human and is divided into two classes, type I MAGEs (MAGEA, B and C) and type II MAGEs (MAGED, E, F, G, H, L and Necdin). MAGEA4 promotes translesion synthesis, a pathway that allows DNA replication across DNA lesion. MAGEC2 facilitates DNA double strand break repair through the phosphorylation of TRIM28, an E3 ubiquitin ligase, on 824 serine by the ataxia telangiectasia-mutated protein kinase (ATM). MAGEG1 is part of the Structural maintenance of chromosomes 5-6 complex and is essential for homologous recombination. MAGED2 has been shown to delocalize after genotoxic stress and it modulates DNA damage response. Our objective was to further investigate the role of MAGEA and MAGED2 proteins in genotoxic stress resistance and DNA damage response in MelJuso cells.We observed that MAGEA-depleted cells were more sensitive to camptothecin, a
topoisomerase I inhibitor, compared to control cells. We also looked at the phosphorylation of histone H2AX, a early marker of DNA double-strand break, during camptothecin treatment and after release from drug. We observed a much stronger phosphorylation of H2AX during camptothecin treatment and, after removing the drug, seemed to disappeare more slowly in cells depleted for MAGEA. All these researches were also carried out in p53-KO MelJuso cells that
we had obtained in our laboratory by CRISPR/Cas9 technology to determine whether or not MAGEA's role depends on p53. We also assessed the role of MAGED2 in genotoxic stress resistance and DNA damage response in context of camptothecin treatment. We observed that MAGED2-depleted cells were more sensitive to camptothecin. Taken together our results show that MAGEA and MAGED2 depletion impact the cell resistance to camptothecin and that these
proteins could play a role in the early events of DNA damage response or in DNA double strand break repair, which still remains to be confirmed.
| la date de réponse | 18 janv. 2019 |
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| langue originale | Anglais |
| L'institution diplômante |
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| Superviseur | Olivier De Backer (Promoteur) |