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Cell cycle-dependent resolution of DNA double-strand breaks repair

ABSTRACT: Damage to genomic DNA, especially as DNA double strand breaks (DSB), elicits prompt activation of DNA damage response (DDR) which arrest cell-cycle either G1/S or G2/M to avoid entering S and M phase with DNA damage. In mammalian organs cells are in both proliferating and quiescent states. Quiescent cells are already arrested in G0, therefore there may be fundamental difference in DDR between proliferating and quiescent cells. To address these differences we studied recruitment of DSB repair factors and resolution of DNA lesions induced at site-specific DSBs occurring at different cell cycle phases, i.e. in asynchronously proliferating, G0, and G1 arrested cells. Strikingly, DSBs occurring in G0 quiescent cells are irreparable with a sustained activation of p53-pathway. Conversely, reentry of G0-damaged cells into cell cycle progression, show a delayed clearance of recruited DNA repair factors bound at DSBs, indicating an inefficient repair when compared to DSBs induced in asynchronously proliferating or G1 cells. Moreover, we found that initial recognition of DSBs and assembly of DSB factors is largely similar at different cell cycle phases. Our study thereby demonstrates the crucial role of cell cycle phases in repair and resolution of DSBs.

ORGANISM(S): Homo sapiens

PROVIDER: GSE71447 | GEO | 2015/12/30

SECONDARY ACCESSION(S): PRJNA291218

REPOSITORIES: GEO

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Project description:Classical non-homologous end-joining (C-NHEJ) is a major mammalian DNA double strand break (DSB) repair pathway. Core C-NHEJ factors, such as XRCC4, are required for joining DSB intermediates of the G1 phase-specific V(D)J recombination reaction in progenitor lymphocytes. Core factors also contribute to joining DSBs in cycling mature B-lineage cells, including DSBs generated during antibody class switch recombination (CSR) and DSBs generated by ionizing radiation (IR). The XLF C-NHEJ factor is dispensable for V(D)J recombination in normal cells, but, due to functional redundancy, is absolutely required for this process in cells deficient for the ATM DSB response factor. The recently identified PAralogue of XRCC4 and XLF (PAXX) factor has homology to these two proteins and variably contributes to IR-induced DSB repair in human and chicken cells. We now report that PAXX is dispensable for joining V(D)J recombination DSBs in G1-arrested mouse pro-B cell lines, dispensable for joining CSR-associated DSBs in a cycling mouse B cell line, and dispensable for normal IR-resistance in both G1-arrested and cycling pro-B lines. However, we find that combined deficiency for PAXX and XLF in G1-arrested pro-B lines abrogates DSB joining during V(D)J recombination and sensitizes the cells to IR exposure. Thus, PAXX provides core C-NHEJ factor-associated functions in the absence of XLF and vice versa in G1-arrested Pro-B cell lines. Finally, we also find that PAXX-deficiency has no impact on V(D)J recombination DSB joining in ATM-deficient pro-B lines. We discuss implications of these findings with respect to potential PAXX and XLF functions in C-NHEJ. Examination of CSR Switch mu-to-alpha junctions from mu bait DSBs using LAM-HTGTS and Illumina Miseq. Two clones of PAXX-/- and XLF-/- and 1 clone of Ligase4-/- were derived from the parental CH12F3 line; the second Ligase4-/- clone was acquired from Keifei Yu. Two clones of XLF-/-PAXX-/-CH12 cells were derived from one of the PAXX-/- clones. Three biological replicates were analyzed for each clone.

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Cell cycle-dependent resolution of DNA double-strand breaks repair

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