title: Cold sensitivity induced by overproduction of UmuDC in Escherichia coli.
abstract: The UmuD and UmuC proteins of Escherichia coli are essential for mutagenesis by UV and most chemicals. Their mode of action is presently unknown. Strains which lack the LexA repressor [lexA(Def)] and contain a pBR322-derived plasmid carrying the umuDC operon overexpress UmuD and UmuC and become cold sensitive (growth at 42 degrees C but not at 30 degrees C). Deletion mapping showed that the umuDC locus on the plasmid is responsible for conferring cold sensitivity. The conditional lethality appeared due to a rapid and reversible inhibition of DNA synthesis at the nonpermissive temperature. Cold sensitivity was enhanced by the increase of NaCl in the medium to 1% and eliminated by 4% ethanol in the medium. Cold sensitivity was partially suppressed by the lon-100 mutation and completely suppressed by the htpR165 mutation.
authors.forename: L
authors.initials: L
authors.lastname: Marsh
authors.forename: G C
authors.initials: GC
authors.lastname: Walker
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D003080:Cold Temperature; D004269:DNA, Bacterial / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D009154:Mutation
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial