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Journal of Bacteriology, December 1998, p. 6269-6275, Vol. 180, No. 23
Department of Molecular, Cellular, and
Developmental Biology, University of Colorado, Boulder, Colorado
80309
Received 8 June 1998/Accepted 29 September 1998
Sister chromatid exchange (SCE) in Escherichia coli
results in the formation of circular dimer chromosomes, which are
converted back to monomers by a compensating exchange at the
dif resolvase site. Recombination at dif is
site specific and can be monitored by utilizing a density label assay
that we recently described. To characterize factors affecting SCE
frequency, we analyzed dimer resolution at the dif site in
a variety of genetic backgrounds and conditions. Recombination at
dif was increased by known hyperrecombinogenic mutations
such as polA, dut, and uvrD. It was
also increased by a fur mutation, which increased oxidative
DNA damage. Recombination at dif was eliminated by a
recA mutation, reflecting the role of RecA in SCE and
virtually all homologous recombination in E. coli.
Interestingly, recombination at dif was reduced to
approximately half of the wild-type levels by single mutations in
either recB or recF, and it was virtually
eliminated when both mutations were present. This result demonstrates
the importance of both RecBCD and RecF to chromosomal recombination
events in wild-type cells.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Sister Chromatid Exchange Frequencies in
Escherichia coli Analyzed by Recombination at the
dif Resolvase Site
and
*
Corresponding author. Mailing address: Dept. of
Molecular, Cellular, and Developmental Biology, University of Colorado,
Boulder, CO 80309. Phone: (303) 492-7952. Fax: (303) 492-7744. E-mail: Peter.Kuempel{at}colorado.edu.
Present address: Fred Hutchinson Cancer Research Center, Seattle,
WA 98104-2092.
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