title: Ablation of PARP-1 does not interfere with the repair of DNA double-strand breaks, but compromises the reactivation of stalled replication forks.
abstract: Poly(ADP-ribose) polymerase-1 (PARP-1) is an abundant DNA end-sensing and binding molecule. Inactivation of PARP-1 by chemicals and genetic mutations slows cell proliferation, increases sister chromatid exchange (SCE), micronuclei formation and chromosome instability, and shortens telomeres. Given its affinity to DNA breaks and temporal occupation on DNA strand break sites, PARP-1 is proposed to prevent inappropriate DNA recombination. We investigated the potential role of PARP-1 in repair of DNA double-strand breaks (DSBs) and stalled replication forks. PARP-1-/- embryonic stem cells and embryonic fibroblast cells exhibited normal repair of DNA DSBs by either homologous recombination (HR) or nonhomologous end-joining (NHEJ) pathways. Inactivation of PARP-1 did not interfere with gene-targeting efficiency in ES cells. However, PARP-1-/- cells were hypersensitive to the replication damage agent hydroxyurea (HU)-induced cell death and exhibited enhanced SCE formation. Ablation of PARP-1 delayed reactivation of stalled replication forks imposed by HU and re-entry into the G2-M phase after HU release. These data indicate that PARP-1 is dispensable in HR induced by DSBs, but is involved in the repair and reactivation of stalled replication forks.
authors.affiliation: International Agency for Research on Cancer, 150 cours Albert-Thomas, Lyon 69008, France.
authors.forename: Yun-Gui
authors.initials: YG
authors.lastname: Yang
authors.forename: Ulrich
authors.initials: U
authors.lastname: Cortes
authors.forename: Srinivas
authors.initials: S
authors.lastname: Patnaik
authors.forename: Maria
authors.initials: M
authors.lastname: Jasin
authors.forename: Zhao-Qi
authors.initials: ZQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D004249:DNA Damage; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000032:analysis; D006918:Hydroxyurea / Q000494:pharmacology; D051379:Mice; D011065:Poly(ADP-ribose) Polymerases / Q000502:physiology*; D051135:Rad51 Recombinase; D011995:Recombination, Genetic
chemical_list: D004268:DNA-Binding Proteins; D011065:Poly(ADP-ribose) Polymerases; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D006918:Hydroxyurea