Human DNA Polymerase ι Utilizes Different Nucleotide Incorporation Mechanisms Dependent upon the Template Base

M. Todd Washington, Robert E. Johnson, Louise Prakash, Satya Prakash

Research output: Contribution to journalArticle

53 Scopus citations


Human DNA polymerase ι (Polι) is a member of the Y family of DNA polymerases involved in translesion DNA synthesis. Polι is highly unusual in that it possesses a high fidelity on template A, but has an unprecedented low fidelity on template T, preferring to misincorporate a G instead of an A. To understand the mechanisms of nucleotide incorporation opposite different template bases by Polι, we have carried out pre-steady-state kinetic analyses of nucleotide incorporation opposite templates A and T. These analyses have revealed that opposite template A, the correct nucleotide is preferred because it is bound tighter and is incorporated faster than the incorrect nucleotides. Opposite template T, however, the correct and incorrect nucleotides are incorporated at very similar rates, and interestingly, the greater efficiency of G misincorporation relative to A incorporation opposite T arises predominantly from the tighter binding of G. Based on these results, we propose that the incipient base pair is accommodated differently in the active site of Polι dependent upon the template base and that when T is the templating base, Polι accommodates the wobble base pair better than the Watson-Crick base pair.

Original languageEnglish (US)
Pages (from-to)936-943
Number of pages8
JournalMolecular and Cellular Biology
Issue number2
StatePublished - Jan 2004


ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

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