title: Poly(ADP-ribose) polymerase in base excision repair: always engaged, but not essential for DNA damage processing.
abstract: Poly(ADP-ribose) polymerase (PARP-1) is an abundant nuclear protein with a high affinity for single- and double-strand DNA breaks. Its binding to strand breaks promotes catalysis of the covalent modification of nuclear proteins with poly(ADP-ribose) synthesised from NAD(+). PARP-1-knockout cells are extremely sensitive to alkylating agents, suggesting the involvement of PARP-1 in base excision repair; however, its role remains unclear. We investigated the dependence of base excision repair pathways on PARP-1 and NAD(+) using whole cell extracts derived from normal and PARP-1 deficient mouse cells and DNA substrates containing abasic sites. In normal extracts the rate of repair was highly dependent on NAD(+). We found that in the absence of NAD(+) repair was slowed down 4-6-fold after incision of the abasic site. We also established that in extracts from PARP-1 deficient mouse cells, repair of both regular and reduced abasic sites was increased with respect to normal extracts and was NAD(+)-independent, suggesting that in both short- and long-patch BER PARP-1 slows down, rather than stimulates, the repair reaction. Our data support the proposal that PARP-1 does not play a major role in catalysis of DNA damage processing via either base excision repair pathway.
authors.affiliation: MRC Radiation and Genome Stability Unit, Harwell, Oxfordshire, OX11 0RD, UK.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Allinson
authors.forename: Irina I
authors.initials: II
authors.lastname: Dianova
authors.forename: Grigory L
authors.initials: GL
authors.lastname: Dianov
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004260:DNA Repair / Q000235:genetics*; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000201:enzymology / Q000502:physiology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011065:Poly(ADP-ribose) Polymerases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D013379:Substrate Specificity
chemical_list: D009838:Oligodeoxyribonucleotides; D011065:Poly(ADP-ribose) Polymerases