title: Involvement of polynucleotide kinase in a poly(ADP-ribose) polymerase-1-dependent DNA double-strand breaks rejoining pathway.
abstract: Efficient DNA double-strand break (DSB) repair is critical for the maintenance of genomic integrity. In mammalian cells, DSBs are preferentially repaired by the non-homologous end-joining pathway relying on DNA-PK activity, but other mechanisms may promote end-joining. We previously described a DSB repair pathway that requires synapsis of DNA ends by poly(ADP-ribose) polymerase-1 (PARP-1) and ligation by the XRCC1/DNA ligase III complex (XL). Here, the repair of non-ligatable DNA ends by this pathway was examined in human cell extracts. The phosphorylation of the 5'-terminal end was shown to represent a limiting step for the repair process. Polynucleotide kinase (hPNK) was identified as the 5'-DNA kinase associated with the PARP-1-dependent end-joining pathway because (i) hPNK was co-recruited to DNA ends together with PARP-1 and XL, (ii) ligation of 5'-OH terminal breaks was compromised in hPNK-depleted extracts and restored upon addition of recombinant hPNK, and (iii) recombinant hPNK was necessary for end-joining of 5'-OH terminal breaks reconstituted with the PARP-1/XL complex. Also, using an assay enabling us to follow the ligation kinetics of each strand of a DSB, we established that the two strands at the junction can be processed and joined independently, so that one strand can be ligated without a ligatable nick on the other strand at the DSB site. Taken together these results reveal functional parallels between the PARP-1 and DNA-PK-dependent end-joining processes.
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, CNRS UMR 5089, Toulouse, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Audebert
authors.forename: Bernard
authors.initials: B
authors.lastname: Salles
authors.forename: Michael
authors.initials: M
authors.lastname: Weinfeld
authors.forename: Patrick
authors.initials: P
authors.lastname: Calsou
mesh_terms: D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D000075223:Poly-ADP-Ribose Binding Proteins; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000378:metabolism*; D000076105:X-ray Repair Cross Complementing Protein 1; D029867:Xenopus Proteins
chemical_list: D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D029867:Xenopus Proteins; D004247:DNA; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011116:Polynucleotide 5'-Hydroxyl-Kinase; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618817:LIG3 protein, human