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PAXX promotes KU accumulation at DNA breaks and is essential for end-joining in XLF-deficient mice.

ABSTRACT: Non-homologous end-joining (NHEJ) is the most prominent DNA double strand break (DSB) repair pathway in mammalian cells. PAXX is the newest NHEJ factor, which shares structural similarity with known NHEJ factors-XRCC4 and XLF. Here we report that PAXX is dispensable for physiological NHEJ in otherwise wild-type mice. Yet Paxx-/- mice require XLF and Xlf-/- mice require PAXX for end-ligation. As such, Xlf-/-Paxx-/- mice display severe genomic instability and neuronal apoptosis, which eventually lead to embryonic lethality. Despite their structural similarities, only Xlf-/- cells, but not Paxx-/- cells require ATM/DNA-PK kinase activity for end-ligation. Mechanistically, PAXX promotes the accumulation of KU at DSBs, while XLF enhances LIG4 recruitment without affecting KU dynamics at DNA breaks in vivo. Together these findings identify the molecular functions of PAXX in KU accumulation at DNA ends and reveal distinct, yet critically complementary functions of PAXX and XLF during NHEJ.

SUBMITTER: Liu X

PROVIDER: S-EPMC5216128 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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PAXX promotes KU accumulation at DNA breaks and is essential for end-joining in XLF-deficient mice.

Liu Xiangyu X Shao Zhengping Z Jiang Wenxia W Lee Brian J BJ Zha Shan S

Nature communications 20170104

Non-homologous end-joining (NHEJ) is the most prominent DNA double strand break (DSB) repair pathway in mammalian cells. PAXX is the newest NHEJ factor, which shares structural similarity with known NHEJ factors-XRCC4 and XLF. Here we report that PAXX is dispensable for physiological NHEJ in otherwise wild-type mice. Yet Paxx-/- mice require XLF and Xlf-/- mice require PAXX for end-ligation. As such, Xlf-/-Paxx-/- mice display severe genomic instabilit ...[more]

PMID: 28051062

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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.

Dataset Information

PAXX promotes KU accumulation at DNA breaks and is essential for end-joining in XLF-deficient mice.

Publications

PAXX promotes KU accumulation at DNA breaks and is essential for end-joining in XLF-deficient mice.

Similar Datasets

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