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Human DNA Polymerase ι Utilizes Different Nucleotide Incorporation Mechanisms Dependent upon the Template Base
Journal article   Open access   Peer reviewed

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

M. Todd Washington, Robert E Johnson, Louise Prakash and Satya Prakash
Molecular and cellular biology, Vol.24(2), pp.936-943
01/15/2004
DOI: 10.1128/MCB.24.2.936-943.2004
PMCID: PMC343821
PMID: 14701763
url
http://doi.org/10.1128/MCB.24.2.936-943.2004View
Open Access

Abstract

ABSTRACT 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.

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