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Molecular and Cellular Biology, December 2006, p. 9555-9563, Vol. 26, No. 24
0270-7306/06/$08.00+0 doi:10.1128/MCB.01671-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
for Mismatch Extension and for Extension Opposite from DNA Lesions
Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1061
Received 6 September 2006/ Returned for modification 24 September 2006/ Accepted 27 September 2006
Rev1, a Y family DNA polymerase (Pol) functions together with Pol
, a B family Pol comprised of the Rev3 catalytic subunit and Rev7 accessory subunit, in promoting translesion DNA synthesis (TLS). Extensive genetic studies with Saccharomyces cerevisiae have indicated a requirement of both Pol
and Rev1 for damage-induced mutagenesis, implicating their involvement in mutagenic TLS. Pol
is specifically adapted to promote the extension step of lesion bypass, as it proficiently extends primer termini opposite DNA lesions, and it is also a proficient extender of mismatched primer termini on undamaged DNAs. Since TLS through UV-induced lesions and various other DNA lesions does not depend upon the DNA-synthetic activity of Rev1, Rev1 must contribute to Pol
-dependent TLS in a nonenzymatic way. Here, we provide evidence for the physical association of Rev1 with Pol
and show that this binding is mediated through the C terminus of Rev1 and the polymerase domain of Rev3. Importantly, a rev1 mutant that lacks the C-terminal 72 residues which inactivate interaction with Rev3 exhibits the same high degree of UV sensitivity and defectiveness in UV-induced mutagenesis as that conferred by the rev1
mutation. We propose that Rev1 binding to Pol
is indispensable for the targeting of Pol
to the replication fork stalled at a DNA lesion. In addition to this structural role, Rev1 binding enhances the proficiency of Pol
for the extension of mismatched primer termini on undamaged DNAs and for the extension of primer termini opposite DNA lesions.
Published ahead of print on 9 October 2006.
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