title: Specific recognition of a multiply phosphorylated motif in the DNA repair scaffold XRCC1 by the FHA domain of human PNK.
abstract: Short-patch repair of DNA single-strand breaks and gaps (SSB) is coordinated by XRCC1, a scaffold protein that recruits the DNA polymerase and DNA ligase required for filling and sealing the damaged strand. XRCC1 can also recruit end-processing enzymes, such as PNK (polynucleotide kinase 3'-phosphatase), Aprataxin and APLF (aprataxin/PNK-like factor), which ensure the availability of a free 3'-hydroxyl on one side of the gap, and a 5'-phosphate group on the other, for the polymerase and ligase reactions respectively. PNK binds to a phosphorylated segment of XRCC1 (between its two C-terminal BRCT domains) via its Forkhead-associated (FHA) domain. We show here, contrary to previous studies, that the FHA domain of PNK binds specifically, and with high affinity to a multiply phosphorylated motif in XRCC1 containing a pSer-pThr dipeptide, and forms a 2:1 PNK:XRCC1 complex. The high-resolution crystal structure of a PNK-FHA-XRCC1 phosphopeptide complex reveals the basis for this unusual bis-phosphopeptide recognition, which is probably a common feature of the known XRCC1-associating end-processing enzymes.
authors.affiliation: Cancer Research UK DNA Repair Enzyme Group, Section of Structural Biology, The Institute of Cancer Research, London SW3 6JB, UK.
authors.forename: Ammar A E
authors.initials: AA
authors.lastname: Ali
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Jukes
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Pearl
authors.forename: Antony W
authors.initials: AW
authors.lastname: Oliver
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D002151:Calorimetry; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D004268:DNA-Binding Proteins; D010748:Phosphopeptides; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; C530380:PNKP protein, human; D017853:Phosphotransferases (Alcohol Group Acceptor); D010744:Phosphoric Monoester Hydrolases; D045643:DNA Repair Enzymes