Vol. 180, Issue 13, 3405-3409, July 1, 1998
1 Centro Nacional de Biotecnología,
Consejo Superior de Investigaciones Científicas, Campus
Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid,
Spain,1 and
2 Institut National de la
Recherche Agronomique Bacillus subtilis recombination-deficient mutants were
constructed by inserting a selectable marker (cat gene)
into the yppB and ypbC coding regions. The
yppB:cat and ypbC:cat
null alleles rendered cells sensitive to DNA-damaging agents, impaired
plasmid transformation (25- and 100-fold), and moderately affected
chromosomal transformation when present in an otherwise
Rec+ B. subtilis strain. The yppB
gene complemented the defect of the recG40 strain.
yppB and ypbC and their respective null alleles were termed "recU" and "recU1"
(recU:cat) and "recS" and
"recS1" (recS:cat),
respectively. The recU and recS mutations were
introduced into rec-deficient strains representative of the
Génétique Microbienne, 78352 Jouy-en-Josas Cedex, France2
(recF),
(addA5 addB72),
(recH342), and
(recG40) epistatic groups.
The recU mutation did not modify the sensitivity of
recH cells to DNA-damaging agents, but it did affect inter-
and intramolecular recombination in recH cells. The
recS mutation did not modify the sensitivity of
addAB cells to DNA-damaging agents, and it marginally
affected recF, recH, and recU
cells. The recS mutation markedly reduced (about 250-fold)
intermolecular recombination in recH cells, and there were
reductions of 10- to 20-fold in recF, addAB,
and recU cells. Intramolecular recombination was blocked in
recS recF, recS addAB, and recS
recU cells. RecU and RecS have no functional counterparts in
Escherichia coli. Altogether, these data indicate that the
recU and recS proteins are required for DNA
repair and intramolecular recombination and that the recF
(
epistatic group), addAB (
), recH (
),
recU (
), and recS genes provide overlapping activities that compensate for the effects of single mutation. We
tentatively placed recS within a new group, termed
"
."
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