title: Structural basis for the inefficient nucleotide incorporation opposite cisplatin-DNA lesion by human DNA polymerase β.
abstract: Human DNA polymerase β (polβ) has been suggested to play a role in cisplatin resistance, especially in polβ-overexpressing cancer cells. Polβ has been shown to accurately albeit slowly bypass the cisplatin-1,2-d(GpG) (Pt-GG) intramolecular cross-link in vitro. Currently, the structural basis for the inefficient Pt-GG bypass mechanism of polβ is unknown. To gain structural insights into the mechanism, we determined two ternary structures of polβ incorporating dCTP opposite the templating Pt-GG lesion in the presence of the active site Mg(2+) or Mn(2+). The Mg(2+)-bound structure shows that the bulky Pt-GG adduct is accommodated in the polβ active site without any steric hindrance. In addition, both guanines of the Pt-GG lesion form Watson-Crick base pairing with the primer terminus dC and the incoming dCTP, providing the structural basis for the accurate bypass of the Pt-GG adduct by polβ. The Mn(2+)-bound structure shows that polβ adopts a catalytically suboptimal semiclosed conformation during the insertion of dCTP opposite the templating Pt-GG, explaining the inefficient replication across the Pt-GG lesion by polβ. Overall, our studies provide the first structural insights into the mechanism of the potential polβ-mediated cisplatin resistance.
authors.affiliation: From the Division of Medicinal Chemistry, College of Pharmacy, The University of Texas, Austin, Texas 78712.
authors.forename: Myong-Chul
authors.initials: MC
authors.lastname: Koag
authors.affiliation: From the Division of Medicinal Chemistry, College of Pharmacy, The University of Texas, Austin, Texas 78712.
authors.forename: Lara
authors.initials: L
authors.lastname: Lai
authors.affiliation: From the Division of Medicinal Chemistry, College of Pharmacy, The University of Texas, Austin, Texas 78712 SeongminLee@austin.utexas.edu.
authors.forename: Seongmin
authors.initials: S
authors.lastname: Lee
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D002945:Cisplatin / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D003570:Cytidine Triphosphate / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D019951:DNA Polymerase beta / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D006147:Guanine / Q000737:chemistry; D006801:Humans; D008274:Magnesium / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism; D009711:Nucleotides / Q000737:chemistry / Q000235:genetics; D017434:Protein Structure, Tertiary
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D009711:Nucleotides; D008345:Manganese; D006147:Guanine; D003570:Cytidine Triphosphate; D004247:DNA; D019951:DNA Polymerase beta; D008274:Magnesium; D002945:Cisplatin
keywords: DNA Damage; DNA Polymerase; DNA Replication; Enzyme Catalysis; Enzyme Structure