title: ATM- and ATR-mediated phosphorylation of XRCC3 regulates DNA double-strand break-induced checkpoint activation and repair.
abstract: The RAD51 paralogs XRCC3 and RAD51C have been implicated in homologous recombination (HR) and DNA damage responses. However, the molecular mechanism(s) by which these paralogs regulate HR and DNA damage signaling remains obscure. Here, we show that an SQ motif serine 225 in XRCC3 is phosphorylated by ATR kinase in an ATM signaling pathway. We find that RAD51C but not XRCC2 is essential for XRCC3 phosphorylation, and this modification follows end resection and is specific to S and G2 phases. XRCC3 phosphorylation is required for chromatin loading of RAD51 and HR-mediated repair of double-strand breaks (DSBs). Notably, in response to DSBs, XRCC3 participates in the intra-S-phase checkpoint following its phosphorylation and in the G2/M checkpoint independently of its phosphorylation. Strikingly, we find that XRCC3 distinctly regulates recovery of stalled and collapsed replication forks such that phosphorylation is required for the HR-mediated recovery of collapsed replication forks but is dispensable for the restart of stalled replication forks. Together, these findings suggest that XRCC3 is a new player in the ATM/ATR-induced DNA damage responses to control checkpoint and HR-mediated repair.
authors: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors: Kumar
authors: K
authors: Somyajit
authors: Shivakumar
authors: S
authors: Basavaraju
authors: Ralph
authors: R
authors: Scully
authors: Ganesh
authors: G
authors: Nagaraju
mesh_terms: D000595:Amino Acid Sequence; D064007:Ataxia Telangiectasia Mutated Proteins; D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007399:Interphase; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016415:Sequence Alignment; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C448305:RAD51C protein, human; D025521:Tumor Suppressor Proteins; C110901:X-ray repair cross complementing protein 3; C113187:XRCC2 protein, human; D004247:DNA; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases