4tus
From Proteopedia
Human DNA polymerase beta inserting dCMPNPP opposite the 5'G of cisplatin crosslinked Gs (Pt-GG2) WITH MANGANESE IN THE ACTIVE SITE.
Structural highlights
Function[DPOLB_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 PubMedHuman DNA polymerase beta (polbeta) has been suggested to play a role in cisplatin resistance, especially in polbeta-overexpressing cancer cells. Polbeta 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 polbeta is unknown. To gain structural insights into the mechanism, we determined two ternary structures of polbeta incorporating dCTP opposite the templating Pt-GG lesion in the presence of the active-site Mg2+ or Mn2+. The Mg2+-bound structure shows that the bulky Pt-GG adduct is accommodated in the polbeta 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 polbeta. The Mn2+-bound structure shows that polbeta adopts a catalytically sub-optimal semi-closed conformation during the insertion of dCTP opposite the templating Pt-GG, explaining the inefficient replication across the Pt-GG lesion by polbeta. Overall, our studies provide the first structural insights into the mechanism of the potential polbeta-mediated cisplatin resistance. Structural Basis for the Inefficient Nucleotide Incorporation Opposite Cisplatin-DNA Lesion by Human DNA Polymerase beta,Koag MC, Lai L, Lee S J Biol Chem. 2014 Sep 18. pii: jbc.M114.605451. PMID:25237188[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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