Work

The I260Q Variant of DNA Polymerase β Extends Mispaired Primer Termini Due to Its Increased Affinity for Deoxynucleotide Triphosphate Substrates

Year: 2008

Type: article

Abstract: DNA polymerase beta plays a key role in base excision repair. We have previously shown that the hydrophobic hinge region of polymerase beta, which is distant from its active site, plays a critical role in the fidelity of DNA synthesis by this enzyme. The I260Q hinge variant of polymerase beta misincorporates nucleotides with a significantly higher catalytic efficiency than the wild-type enzyme. In the study described here, we show that I260Q extends mispaired primer termini. The kinetic basis for extension of mispairs is defective discrimination by I260Q at the level of ground-state binding of the dNTP substrate. Our results suggest that the hydrophobic hinge region influences the geometry of the dNTP binding pocket exclusively. Because the DNA forms part of the binding pocket, our data are also consistent with the interpretation that the mispaired primer terminus affects the geometry of the dNTP binding pocket such that the I260Q variant has a higher affinity for the incoming dNTP than wild-type polymerase beta.

Source: Biochemistry

DOI: 10.1021/bi8011548

Authors: Shibani Dalal, Daniela Starcevic, Joachim Jaeger, Joann B. Sweasy

Institutions: New York State Department of Health, Wadsworth Center, Yale University

Language: English

Topic: DNA Repair Mechanisms

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: green

Funder: National Cancer Institute

Awards: DNA Polymerase Beta and Mutagenesis, G2069265750