6u6b | pdb_00006u6b
Structure of human DNA polymerase beta misinserting dAMPNPP opposite the 5'G of the cisplatin Pt-GG intrastrand crosslink with Manganese in the active site
Structural highlights
FunctionDPOLB_HUMAN Repair polymerase that plays a key role in base-excision repair. Has 5'-deoxyribose-5-phosphate lyase (dRP lyase) activity that removes the 5' sugar phosphate and also acts as a DNA polymerase that adds one nucleotide to the 3' end of the arising single-nucleotide gap. Conducts 'gap-filling' DNA synthesis in a stepwise distributive fashion rather than in a processive fashion as for other DNA polymerases.[1] [2] [3] [4] Publication Abstract from PubMedThe cisplatin-1,2-d(GpG) (Pt-GG) intrastrand cross-link is the predominant DNA lesion generated by cisplatin. Cisplatin has been shown to predominantly induce G to T mutations and Pt-GG permits significant misincorporation of dATP by human DNA polymerase beta (polbeta). In agreement, polbeta overexpression, which is frequently observed in cancer cells, is linked to cisplatin resistance and a mutator phenotype. However, the structural basis for the misincorporation of dATP opposite Pt-GG is unknown. Here, we report the first structures of a DNA polymerase inaccurately bypassing Pt-GG. We solved two structures of polbeta misincorporating dATP opposite the 5'-dG of Pt-GG in the presence of Mg2+ or Mn2+. The Mg2+-bound structure exhibits a sub-optimal conformation for catalysis, while the Mn2+-bound structure is in a catalytically more favorable semi-closed conformation. In both structures, dATP does not form a coplanar base pairing with Pt-GG. In the polbeta active site, the syn-dATP opposite Pt-GG appears to be stabilized by protein templating and pi stacking interactions, which resembles the polbeta-mediated dATP incorporation opposite an abasic site. Overall, our results suggest that the templating Pt-GG in the polbeta active site behaves like an abasic site, promoting the insertion of dATP in a non-instructional manner. Structural insights into the promutagenic bypass of the major cisplatin-induced DNA lesion.,Ouzon-Shubeita H, Vilas CK, Lee S Biochem J. 2020 Mar 13;477(5):937-951. doi: 10.1042/BCJ20190906. PMID:32039434[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||||
