File(s) not publicly available
XRCC1 stimulates polynucleotide kinase by enhancing its damage discrimination and displacement from DNA repair intermediates
journal contributionposted on 2023-06-07, 21:00 authored by Rajam S Mani, Mesfin Fanta, Feridoun Karimi-Busheri, Elizabeth Silver, César A Virgen, Keith CaldecottKeith Caldecott, Carol E Cass, Michael Weinfeld
Human polynucleotide kinase (hPNK) is required for processing and rejoining DNA strand break termini. The 5'-DNA kinase and 3'-phosphatase activities of hPNK can be stimulated by the ¿scaffold¿ protein XRCC1, but the mechanism remains to be fully elucidated. Using a variety of fluorescence techniques, we examined the interaction of hPNK with XRCC1 and substrates that model DNA single-strand breaks. hPNK binding to substrates with 5'-OH termini was only ~5-fold tighter than that to identical DNA molecules with 5'-phosphate termini, suggesting that hPNK remains bound to the product of its enzymatic activity. The presence of XRCC1 did not influence the binding of hPNK to substrates with 5'-OH termini, but sharply reduced the interaction of hPNK with DNA bearing a 5'-phosphate terminus. These data, together with kinetic data obtained at limiting enzyme concentration, indicate a dual function for the interaction of XRCC1 with hPNK. First, XRCC1 enhances the capacity of hPNK to discriminate between strand breaks with 5'-OH termini and those with 5'-phosphate termini; and second, XRCC1 stimulates hPNK activity by displacing hPNK from the phosphorylated DNA product.
JournalJournal of Biological Chemistry
Department affiliated with
- Sussex Centre for Genome Damage Stability Publications
Full text available