REPAIRCHROM

The repair of DNA lesions involves at early stages an active remodeling of the chromatin architecture. If the exact function of this mechanism remains unclear, it is essential for an efficient correction of the DNA breaks. The poly-ADP-ribosylation signaling pathway, and in particular the PAR-dependent remodelers, play a central role during these chromatin reorganization mechanisms associated with the activation of the DNA damage response of the cell. During this project, we aim not only at establishing a full description of these chromatin remodeling processes but also at better understanding their impact on the subsequent DNA repair steps. In this context, we will focus more specifically on the role of the PAR-dependent remodelers. To reach this goal, we setup a consortium gathering three research teams with complementary expertise. This consortium will establish a multi-scale analysis framework allowing to characterize the different folding levels of the chromatin: from the nucleosomes to the topologically associated domains (TADs). Dynamics at the nucleosome scale will be assessed by combining ATAC-seq with single-molecule imaging techniques: fluorescence correlation spectroscopy and single molecule tracking. At higher scales, the dynamics of chromatin loops and TADs will be monitored by chromatin conformation capture (4C-seq) and by tracking the movements of single TADs in the nucleus of living cells. These different methods will be used to analyze the changes affecting the chromatin structure in the vicinity of DNA breaks induced by laser irradiation or by restriction enzymes. Next, we will analyze the role of the PAR-dependent remodelers during these modifications of the chromatin structure. Finally, we will study how chromatin remodeling events specific to these remodelers influence the subsequent steps of the repair mechanisms. We will analyze in particular their impact on the regulation of the DNA end resection at the double-strand breaks. The switch between the initiation of this process or its inhibition determines whether the break will then be repaired by homologous recombination (HR) or by non-homologous end-joining (NHEJ). We will analyze the impact of knocking-down the PAR-dependent remodelers on the recruitment of the proteins regulating the initiation of the resection process. We will also monitor how these knock-downs affect the HR/NHEJ balance and influence the efficiency and the fidelity of the repair process. Altogether, these different results will allow us to uncover the specific function of the early chromatin remodeling mechanisms in the maintenance of genome integrity. By contributing to a better understanding of the role of the PARylation signaling pathway during the DNA repair process, our project may contribute to identify new therapeutic targets for cancer treatments. Moreover, given that many tumor cells display a perturbed chromatin architecture, our project will help to establish the impact of these perturbations on the efficiency of the repair mechanisms in these cells.