6bs1
From Proteopedia
Crystal Structure of Human DNA polymerase kappa in complex with DNA containing the major cisplatin lesion
Structural highlights
Function[POLK_HUMAN] DNA polymerase specifically involved in DNA repair. Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls. Depending on the context, it inserts the correct base, but causes frequent base transitions, transversions and frameshifts. Lacks 3'-5' proofreading exonuclease activity. Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but does not have lyase activity.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedCisplatin (cis-diamminedichloroplatinum) is a common chemotherapeutic drug that reacts with the N7 atoms of adjacent guanines in DNA to form the Pt-1,2-d(GpG) intrastrand cross-link (Pt-GG), a major product to block DNA replication. Translesion DNA synthesis has been implicated in chemoresistance during cisplatin treatment of cancer due to Pt-GG lesion bypass. Gene knockdown studies in human cells have indicated a role for polkappa during translesion synthesis of the Pt-GG lesion. However, the bypass activity of polkappa with cisplatin lesions has not been well characterized. In this study, we investigated polkappa's ability to bypass Pt-GG lesion in vitro and determined two crystal structures of polkappa in complex with Pt-GG DNA. The ternary complex structures represent two consecutive stages of lesion bypass: nucleotide insertion opposite the 5'G (Pt-GG2) and primer extension immediately after the lesion (Pt-GG3). Our biochemical data showed that polkappa is very efficient and accurate in extending DNA primers after the first G of the Pt-GG lesion. The structures demonstrate that the efficiency and accuracy is achieved by stably accommodating the bases with the cisplatin adduct in the active site for proper Watson-Crick base pairing with the incoming nucleotide in both the second insertion and post-insertion complexes. Our studies suggest that polkappa works as an extender for efficient replication of the Pt-GG lesion in cells. This work holds promise for considering polkappa, along with poleta, as potential targets for drug design, which together could improve the efficacy of cisplatin treatment for cancer therapy. Structural Basis for Human DNA Polymerase Kappa to Bypass Cisplatin Intrastrand Cross-Link (Pt-GG) Lesion as an Efficient and Accurate Extender.,Jha V, Ling H J Mol Biol. 2018 May 25;430(11):1577-1589. doi: 10.1016/j.jmb.2018.04.023. Epub, 2018 Apr 30. PMID:29715472[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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