Abstract
Combined deficiencies of poly(ADP)ribosyl polymerase 1 (PARP1) and ataxia telangiectasia mutated (ATM) result in synthetic lethality and, in the mouse, early embryonic death. Here, we investigated the genetic requirements for this lethality via analysis of mice deficient for PARP1 and either of two ATM-regulated DNA damage response (DDR) factors: histone H2AX and 53BP1. We found that, like ATM, H2AX is essential for viability in a PARP1-deficient background. In contrast, deficiency for 53BP1 modestly exacerbates phenotypes of growth retardation, genomic instability, and organismal radiosensitivity observed in PARP1-deficient mice. To gain mechanistic insights into these different phenotypes, we examined roles for 53BP1 in the repair of replication-associated double-strand breaks (DSBs) in several cellular contexts. We show that 53BP1 is required for DNA-PKcs-dependent repair of hydroxyurea (HU)-induced DSBs but dispensable for RPA/RAD51-dependent DSB repair in the same setting. Moreover, repair of mitomycin C (MMC)-induced DSBs and sister chromatid exchanges (SCEs), two RAD51-dependent processes, are 53BP1 independent. Overall, our findings define 53BP1 as a main facilitator of nonhomologous end joining (NHEJ) during the S phase of the cell cycle, beyond highly specialized lymphocyte rearrangements. These findings have important implications for our understanding of the mechanisms whereby ATM-regulated DDR prevents human aging and cancer.
MeSH terms
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Aging / physiology
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Animals
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B-Lymphocytes / cytology
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B-Lymphocytes / metabolism
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Chromosomal Proteins, Non-Histone
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DNA / drug effects
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DNA / genetics
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DNA / metabolism
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DNA / radiation effects
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DNA Breaks, Double-Stranded / drug effects
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DNA Breaks, Double-Stranded / radiation effects
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DNA Repair
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DNA-Activated Protein Kinase / genetics
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DNA-Activated Protein Kinase / metabolism
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Female
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Genome*
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Genomic Instability
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Histones / genetics
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Histones / metabolism*
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Humans
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Hydroxyurea / pharmacology
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In Situ Hybridization, Fluorescence
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Male
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Mice
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Mice, Knockout
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Mitomycin / pharmacology
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Nucleic Acid Synthesis Inhibitors / pharmacology
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Phenotype
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases / genetics
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Poly(ADP-ribose) Polymerases / metabolism*
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Rad51 Recombinase / genetics
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Rad51 Recombinase / metabolism
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Radiation, Ionizing
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Sister Chromatid Exchange
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Tumor Suppressor p53-Binding Protein 1
Substances
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Chromosomal Proteins, Non-Histone
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DNA-Binding Proteins
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H2AX protein, mouse
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Histones
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Intracellular Signaling Peptides and Proteins
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Nuclear Proteins
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Nucleic Acid Synthesis Inhibitors
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Trp53bp1 protein, mouse
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Tumor Suppressor p53-Binding Protein 1
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Mitomycin
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DNA
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Parp1 protein, mouse
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases
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DNA-Activated Protein Kinase
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Prkdc protein, mouse
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Rad51 Recombinase
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Hydroxyurea