title: In Vitro Lesion Bypass Studies of O(4)-Alkylthymidines with Human DNA Polymerase η.
abstract: Environmental exposure and endogenous metabolism can give rise to DNA alkylation. Among alkylated nucleosides, O(4)-alkylthymidine (O(4)-alkyldT) lesions are poorly repaired in mammalian systems and may compromise the efficiency and fidelity of cellular DNA replication. To cope with replication-stalling DNA lesions, cells are equipped with translesion synthesis DNA polymerases that are capable of bypassing various DNA lesions. In this study, we assessed human DNA polymerase η (Pol η)-mediated bypass of various O(4)-alkyldT lesions, with the alkyl group being Me, Et, nPr, iPr, nBu, iBu, (R)-sBu, or (S)-sBu, in template DNA by conducting primer extension and steady-state kinetic assays. Our primer extension assay results revealed that human Pol η, but not human polymerases κ and ι or yeast polymerase ζ, was capable of bypassing all O(4)-alkyldT lesions and extending the primer to generate full-length replication products. Data from steady-state kinetic measurements showed that Pol η preferentially misincorporated dGMP opposite O(4)-alkyldT lesions with a straight-chain alkyl group. The nucleotide misincorporation opposite most lesions with a branched-chain alkyl group was, however, not selective, where dCMP, dGMP, and dTMP were inserted at similar efficiencies opposite O(4)-iPrdT, O(4)-iBudT, and O(4)-(R)-sBudT. These results provide important knowledge about the effects of the length and structure of the alkyl group in O(4)-alkyldT lesions on the fidelity and efficiency of DNA replication mediated by human Pol η.
authors.affiliation: Environmental Toxicology Graduate Program, ‡Department of Chemistry, University of California , Riverside, California 92521-0403, United States.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Williams
authors.affiliation: Environmental Toxicology Graduate Program, ‡Department of Chemistry, University of California , Riverside, California 92521-0403, United States.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Environmental Toxicology Graduate Program, ‡Department of Chemistry, University of California , Riverside, California 92521-0403, United States.
authors.forename: Jiabin
authors.initials: J
authors.lastname: Wu
authors.affiliation: Environmental Toxicology Graduate Program, ‡Department of Chemistry, University of California , Riverside, California 92521-0403, United States.
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000478:Alkylation; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D011994:Recombinant Proteins / Q000378:metabolism; D013936:Thymidine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism*; D000099270:Y-Family DNA Polymerases
chemical_list: D004247:DNA; D004259:DNA-Directed DNA Polymerase; D011994:Recombinant Proteins; D013936:Thymidine; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases