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Journal of Bacteriology, December 2000, p. 6598-6604, Vol. 182, No. 23
Laboratory of Chemical Biology, Department of
Pharmacological Sciences, SUNY at Stony Brook, Stony Brook, New
York 11794-8651
Received 14 June 2000/Accepted 12 September 2000
To study the mechanisms by which Escherichia coli
modulates the genotoxic effects of DNA damage, a novel system has been
developed which permits quantitative measurements of various E. coli pathways involved in mutagenesis and DNA repair. Events
measured include fidelity and efficiency of translesion DNA synthesis,
excision repair, and recombination repair. Our strategy involves
heteroduplex plasmid DNA bearing a single site-specific DNA adduct and
several mismatched regions. The plasmid replicates in a mismatch
repair-deficient host with the mismatches serving as strand-specific
markers. Analysis of progeny plasmid DNA for linkage of the
strand-specific markers identifies the pathway from which the plasmid
is derived. Using this approach, a single
1,N6-ethenodeoxyadenosine adduct was shown to
be repaired inefficiently by excision repair, to inhibit DNA synthesis
by approximately 80 to 90%, and to direct the incorporation of correct
dTMP opposite this adduct. This approach is especially useful in
analyzing the damage avoidance-tolerance mechanisms. Our results also
show that (i) progeny derived from the damage avoidance-tolerance
pathway(s) accounts for more than 15% of all progeny; (ii) this
pathway(s) requires functional recA, recF,
recO, and recR genes, suggesting the mechanism
to be daughter strand gap repair; (iii) the ruvABC genes or
the recG gene is also required; and (iv) the RecG pathway appears to be more active than the RuvABC pathway. Based on these results, the mechanism of the damage avoidance-tolerance pathway is discussed.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Escherichia coli Responses to a Single
DNA Adduct

*
Corresponding author. Mailing address: Laboratory of
Chemical Biology, Department of Pharmacological Sciences, SUNY at Stony Brook, Stony Brook, NY 11794-8651. Phone: (631) 444-3082. Fax: (631)
444-7641. E-mail: maki{at}pharm.sunysb.edu.
Present address: Wyeth-Ayerst Research, Pearl River, NY 10965.
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