title: Lesion Orientation ofO4-Alkylthymidine Influences Replication by Human DNA Polymeraseη.
abstract: DNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases.O4-Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4-O4bond on processing by human DNA polymeraseη(hPolη) was studied for oligonucleotides containingO4-methylthymidine,O4-ethylthymidine, and analogs restricting theO4-methylene group in ananti-orientation. Primer extension assays revealed that theO4-alkyl orientation influences hPolηbypass. Crystal structures of hPolη•DNA•dNTP ternary complexes withO4-methyl- orO4-ethylthymidine in the template strand showed the nucleobase of the former lodged near the ceiling of the active site, with thesyn-O4-methyl group engaged in extensive hydrophobic interactions. This unique arrangement forO4-methylthymidine with hPolη, inaccessible for the other analogs due to steric/conformational restriction, is consistent with differences observed for nucleotide incorporation and supports the concept that lesion conformation influences extension across DNA damage. Together, these results provide mechanistic insights on the mutagenicity ofO4MedT andO4EtdT when acted upon by hPolη.
authors: Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada.
authors: D K
authors: DK
authors: O'Flaherty
authors: Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States.
authors: A
authors: A
authors: Patra
authors: Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States.
authors: Y
authors: Y
authors: Su
authors: Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States.
authors: F P
authors: FP
authors: Guengerich
authors: Department of Biochemistry, Vanderbilt Institute of Chemical Biology, and Center for Structural Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States.
authors: M
authors: M
authors: Egli
authors: Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec H4B1R6, Canada.
authors: C J
authors: CJ
authors: Wilds