Gérard MazónInstitut Gustave Roussy - CNRS / Université Paris-Sud
Mes recherches
I obtained my PhD in the Autonomous University of Barcelona (Spain) in 2004 and since then I developed my career in the field of the DNA repair mechanisms, with postdocs in France (UPR3081, Marseille) and the USA (Columbia University, NY). In Marseille, I characterized the details of an enhanced nucleotide excision repair of alkylation damages by the action of an alkyl-transferase like protein (eATL) and I also developed a new methodology to insert single-defined DNA lesions in the chromosome of E.coli. At Columbia University, I worked in the yeast model system to understand the mechanisms that cells use to regulate crossover (CO) levels during mitotic recombination double-strand break repair using genetic and physical assays. I have lead an ATIP-Avenir team at Gustave Roussy between 2014-2019 where I worked in the characterization of the regulation of nucleases and helicases in the late steps of HR. We found a new the mechanism of regulation of the nuclease Yen1 by Ubiquitin and SUMO post-translational modifications (PTMs). I am now leading a larger team that will integrate electron microscopy; biochemistry and molecular biology approaches to better understand the regulation of the Rad51 nucleofilament and the proteins involved in dismantling joint-molecule DNA intermediates.
Mon projet ATIP-Avenir
Crossover control during mitotic recombination
During Homologous Recombination repair (HR) of double-strand breaks (DSBs), crossed-stranded DNA structures can be formed between the broken chromosome and the homologous template (Holliday junctions, HJs). Cleavage of the HJs by different endonucleases can generate Crossovers (CO). When CO
occur between non-sister chromatids or homology present in other chromosomes this can result in loss of heterozygosity (LOH) or genome rearrangements, events associated with tumorigenesis. Two pathways enforce non-crossover repair outcomes during HR: the synthesis-dependent strand annealing pathway (SDSA) where a helicase displaces D-loop intermediates and the Sgs1/BLM helicase dissolution pathway to remove dHJ. My project aims at elucidating the role of the yeast helicase Mph1, the ortholog of Fanconi Anemia related helicase FANCM, and its interplay with structure-selective nucleases (SSNs) during the late steps of HR in mitotic cells. Mph1 has been proposed to play an important role in D-loop dissociation to prevent crossovers during DSB repair. However, no thorough characterization of such a role has been described to date. My proposal will explore the role of Mph1 in preventing crossovers/translocations formed during DSB repair and its interaction with the SSNs involved in CO formation. Preliminary data suggest a strong genetic interaction between Mph1 and SSNs, which renders cells extremely sensitive to ionizing radiation. The influence of the extent of homology available for repair in the role of Mph1 and SSNs will also be studied. Furthermore, I will address the factors involved in regulation of both Mph1 and SSNs, and study how to inhibit either their recruitment or activity. Research in yeast is aimed at establishing solid foundations at the mechanistic level. Human cell lines will then be used to confirm these findings in a more significant context for cancer research and to understand the functions of proteins related to cancer predisposition as FANCM, MUS81 and GEN1.