title: Phosphorylation of Exo1 modulates homologous recombination repair of DNA double-strand breaks.
abstract: DNA double-strand break (DSB) repair via the homologous recombination pathway is a multi-stage process, which results in repair of the DSB without loss of genetic information or fidelity. One essential step in this process is the generation of extended single-stranded DNA (ssDNA) regions at the break site. This ssDNA serves to induce cell cycle checkpoints and is required for Rad51 mediated strand invasion of the sister chromatid. Here, we show that human Exonuclease 1 (Exo1) is required for the normal repair of DSBs by HR. Cells depleted of Exo1 show chromosomal instability and hypersensitivity to ionising radiation (IR) exposure. We find that Exo1 accumulates rapidly at DSBs and is required for the recruitment of RPA and Rad51 to sites of DSBs, suggesting a role for Exo1 in ssDNA generation. Interestingly, the phosphorylation of Exo1 by ATM appears to regulate the activity of Exo1 following resection, allowing optimal Rad51 loading and the completion of HR repair. These data establish a role for Exo1 in resection of DSBs in human cells, highlighting the critical requirement of Exo1 for DSB repair via HR and thus the maintenance of genomic stability.
authors.affiliation: Signal Transduction Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Bolderson
authors.forename: Nozomi
authors.initials: N
authors.lastname: Tomimatsu
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Richard
authors.forename: Didier
authors.initials: D
authors.lastname: Boucher
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Tej K
authors.initials: TK
authors.lastname: Pandita
authors.forename: Sandeep
authors.initials: S
authors.lastname: Burma
authors.forename: Kum Kum
authors.initials: KK
authors.lastname: Khanna
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D002869:Chromosome Aberrations; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D055785:Gene Knockdown Techniques; D006657:Histones / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051135:Rad51 Recombinase / Q000378:metabolism; D011839:Radiation, Ionizing; D011995:Recombination, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C114331:EXO1 protein, human; D005090:Exodeoxyribonucleases; D045643:DNA Repair Enzymes