title: ATR-p53 restricts homologous recombination in response to replicative stress but does not limit DNA interstrand crosslink repair in lung cancer cells.
abstract: Homologous recombination (HR) is required for the restart of collapsed DNA replication forks and error-free repair of DNA double-strand breaks (DSB). However, unscheduled or hyperactive HR may lead to genomic instability and promote cancer development. The cellular factors that restrict HR processes in mammalian cells are only beginning to be elucidated. The tumor suppressor p53 has been implicated in the suppression of HR though it has remained unclear why p53, as the guardian of the genome, would impair an error-free repair process. Here, we show for the first time that p53 downregulates foci formation of the RAD51 recombinase in response to replicative stress in H1299 lung cancer cells in a manner that is independent of its role as a transcription factor. We find that this downregulation of HR is not only completely dependent on the binding site of p53 with replication protein A but also the ATR/ATM serine 15 phosphorylation site. Genetic analysis suggests that ATR but not ATM kinase modulates p53's function in HR. The suppression of HR by p53 can be bypassed under experimental conditions that cause DSB either directly or indirectly, in line with p53's role as a guardian of the genome. As a result, transactivation-inactive p53 does not compromise the resistance of H1299 cells to the interstrand crosslinking agent mitomycin C. Altogether, our data support a model in which p53 plays an anti-recombinogenic role in the ATR-dependent mammalian replication checkpoint but does not impair a cell's ability to use HR for the removal of DSB induced by cytotoxic agents.
authors.affiliation: Laboratory of Cellular and Molecular Radiation Oncology, Massachusetts General Hospital Cancer Center, Charlestown, Massachusetts, United States of America.
authors.forename: Bianca M
authors.initials: BM
authors.lastname: Sirbu
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Lachmayer
authors.forename: Verena
authors.initials: V
authors.lastname: Wülfing
authors.forename: Lara M
authors.initials: LM
authors.lastname: Marten
authors.forename: Katie E
authors.initials: KE
authors.lastname: Clarkson
authors.forename: Linda W
authors.initials: LW
authors.lastname: Lee
authors.forename: Liliana
authors.initials: L
authors.lastname: Gheorghiu
authors.forename: Lee
authors.initials: L
authors.lastname: Zou
authors.forename: Simon N
authors.initials: SN
authors.lastname: Powell
authors.forename: Jochen
authors.initials: J
authors.lastname: Dahm-Daphi
authors.forename: Henning
authors.initials: H
authors.lastname: Willers
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects; D005434:Flow Cytometry; D059765:Homologous Recombination; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016685:Mitomycin / Q000494:pharmacology; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D013936:Thymidine / Q000494:pharmacology; D015533:Transcriptional Activation / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D051135:Rad51 Recombinase; D013936:Thymidine