Human DNA polymerase iota promiscuous mismatch extension

J Biol Chem. 2001 Aug 17;276(33):30615-22. doi: 10.1074/jbc.M102694200. Epub 2001 Jun 11.

Abstract

Human DNA polymerase iota is a low-fidelity template copier that preferentially catalyzes the incorporation of the wobble base G, rather than the Watson-Crick base A, opposite template T (Tissier, A., McDonald, J. P., Frank, E. G., and Woodgate, R. (2000) Genes Dev. 14, 1642-1650; Johnson, R. E., Washington, M. T., Haracska, L., Prakash, S., and Prakash, L. (2000) Nature 406, 1015-1019; Zhang, Y., Yuan, F., Wu, X., and Wang, Z. (2000) Mol. Cell. Biol. 20, 7099-7108). Here, we report on its ability to extend all 12 possible mispairs and 4 correct pairs in different sequence contexts. Extension from both matched and mismatched primer termini is generally most efficient and accurate when A is the next template base. In contrast, extension occurs less efficiently and accurately when T is the target template base. A striking exception occurs during extension of a G:T mispair, where the enzyme switches specificity, "preferring" to make a correct A:T base pair immediately downstream from an originally favored G:T mispair. Polymerase iota generates a variety of single and tandem mispairs with high frequency, implying that it may act as a strong mutator when copying undamaged DNA templates in vivo. Even so, its limited ability to catalyze extension from a relatively stable primer/template containing a "buried" mismatch suggests that polymerase iota-catalyzed errors are confined to short template regions.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Pair Mismatch*
  • Catalysis
  • DNA / metabolism*
  • DNA-Directed DNA Polymerase / metabolism*
  • Humans

Substances

  • DNA
  • DNA polymerase iota
  • DNA-Directed DNA Polymerase