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J. Bacteriol. doi:10.1128/JB.01777-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

UvrD limits the number and intensities of RecA-GFP structures in Escherichia coli K-12

Molecular and Cellular Biology Graduate Program, Morrill Science Center, University of Massachusetts at Amherst, Amherst, MA 01003, Department of Microbiology, Morrill Science Center IV N203, University of Massachusetts at Amherst, Amherst, MA 01003

^* To whom correspondence should be addressed. Email: sandler{at}microbio.umass.edu.

	Abstract

RecA is important for recombination, DNA repair and SOS induction. In E. coli, RecBCD, RecFOR and RecJQ prepare DNA substrates onto which RecA binds. UvrD is a 3' to 5' helicase that participates in Methyl-Directed Mismatch Repair (MMR) and Nucleotide Excision Repair (NER). UvrD deletion mutants are sensitive to UV irradiation, hyper-mutable and hyper-rec. In vitro, UvrD can dissociate RecA from ssDNA. Other experiments suggest that UvrD removes RecA from DNA where it promotes unproductive reactions. To test if UvrD limits the number and or the size of RecA-DNA structures in vivo, an uvrD mutation was combined with recA-gfp. This recA allele allows the number of RecA structures and the amount of RecA at these structures to be assayed in living cells. UvrD mutants show a three-fold increase in the number of RecA-GFP foci and these foci are, on average, nearly two-fold higher in relative intensity. The increased number of RecA-GFP foci in the uvrD mutant is dependent on recF, recO, recR, recJ and recQ. The increase in average relative intensity is dependent on recO and recQ. These data support an in vivo role for UvrD in removing RecA from the DNA.