期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2005
卷号：102
期号：30
页码：10466-10471
DOI：10.1073/pnas.0503859102
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Because of the near geometric identity of Watson-Crick (W-C) G{middle dot}C and A{middle dot}T base pairs, a given DNA polymerase forms the four possible correct base pairs with nearly identical catalytic efficiencies. However, human DNA polymerase {iota} (Pol{iota}), a member of the Y family of DNA polymerases, exhibits a marked template specificity, being more efficient at incorporating the correct nucleotide opposite template purines than opposite pyrimidines. By using 7-deazaadenine and 7-deazaguanine as the templating residues, which disrupt Hoogsteen base pair formation, we show that, unlike the other DNA polymerases belonging to the A, B, or Y family, DNA synthesis by Pol{iota} is severely inhibited by these N7-modified bases. These observations provide biochemical evidence that, during normal DNA synthesis, template purines adopt a syn conformation in the Pol{iota} active site, enabling the formation of a Hoogsteen base pair with the incoming pyrimidine nucleotide. Additionally, mutational studies with Leu-62, which lies in close proximity to the templating residue in the Pol{iota} ternary complex, have indicated that both factors, steric constraints within the active site and the stability provided by the hydrogen bonds in the Hoogsteen base pair, contribute to the efficiency of correct nucleotide incorporation opposite template purines by Pol{iota}.
关键词：translesion DNA synthesis ; 7-deaza purines ; syn and anti conformations
