title: Involvement of ATM in homologous recombination after end resection and RAD51 nucleofilament formation.
abstract: Ataxia-telangiectasia mutated (ATM) is needed for the initiation of the double-strand break (DSB) repair by homologous recombination (HR). ATM triggers DSB end resection by stimulating the nucleolytic activity of CtIP and MRE11 to generate 3'-ssDNA overhangs, followed by RPA loading and RAD51 nucleofilament formation. Here we show for the first time that ATM is also needed for later steps in HR after RAD51 nucleofilament formation. Inhibition of ATM after completion of end resection did not affect RAD51 nucleofilament formation, but resulted in HR deficiency as evidenced by (i) an increase in the number of residual RAD51/γH2AX foci in both S and G2 cells, (ii) the decrease in HR efficiency as detected by HR repair substrate (pGC), (iii) a reduced SCE rate and (iv) the radiosensitization of cells by PARP inhibition. This newly described role for ATM was found to be dispensable in heterochromatin-associated DSB repair, as KAP1-depletion did not alleviate the HR-deficiency when ATM was inhibited after end resection. Moreover, we demonstrated that ATR can partly compensate for the deficiency in early, but not in later, steps of HR upon ATM inhibition. Taken together, we describe here for the first time that ATM is needed not only for the initiation but also for the completion of HR.
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Bakr
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany Department of Oncology, Hematology and Bone Marrow Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Oing
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Köcher
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Borgmann
authors.affiliation: Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Hamburg 20251, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Dornreiter
authors.affiliation: Department of Radiotherapy & Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Petersen
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Dikomey
authors.affiliation: Laboratory of Radiobiology & Experimental Radiooncology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany Tumor Biology Department, National Cancer Institute, Cairo University, Cairo 11796, Egypt wmansour@uke.de.
authors.forename: W Y
authors.initials: WY
authors.lastname: Mansour
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D004843:Epistasis, Genetic; D016195:G2 Phase; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism; D059765:Homologous Recombination / Q000187:drug effects; D006801:Humans; D000076228:MRE11 Homologue Protein; D009025:Morpholines / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology; D051135:Rad51 Recombinase / Q000378:metabolism*; D016196:S Phase; D013871:Thiones / Q000494:pharmacology
chemical_list: C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; C526365:6-(4-hydroxyphenyl)-2-thioxo-2,3-dihydro-4(1H)-pyrimidinone; D004268:DNA-Binding Proteins; D006570:Heterochromatin; C121766:MRE11 protein, human; D009025:Morpholines; D011744:Pyrimidinones; D011753:Pyrones; D013871:Thiones; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D000076228:MRE11 Homologue Protein