Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Your Environment. Your Health.

Publication Detail

Title: New mutations in cloned Escherichia coli umuDC genes: novel phenotypes of strains carrying a umuC125 plasmid.

Authors: Marsh, L; Nohmi, T; Hinton, S; Walker, G C

Published In Mutat Res, (1991 Sep-Oct)

Abstract: The umuDC locus of Escherichia coli is required for most mutagenesis by UV and many chemicals. Mutations in E. coli umuDC genes cloned on pBR322-derived plasmids were isolated by two methods. First, spontaneously-arising mutant umuDC plasmids that failed to confer cold-sensitive growth on a lexA51(Def) strain were isolated by selection. Second, mutant umuDC plasmids that affected apparent mutant yield after UV-irradiation in a strain carrying umuD+C+ in the chromosome were isolated by screening hydroxylamine-mutagenized umuD+C+ plasmids. pBR322-derived umuD+C+ plasmids inhibited the induction of the SOS response of lexA+ strains as measured by expression of din::Mu dl(lac Ap) fusions but most mutant plasmids did not. Mutant plasmids defective in complementation of chromosomal umuD44, umuC36, or both were found among those selected for failure to confer cold-sensitivity, whereas those identified by the screening procedure yielded mostly mutant plasmids with more complex phenotypes. We studied in greater detail a plasmid, pLM109, carrying the umuC125 mutation. This plasmid increased the sensitivity of lexA+ strains to killing by UV-irradiation but was able to complement the deficiencies of umuC mutants in UV mutagenesis. pLM109 failed to confer cold-sensitive growth on lexA(Def) strains but inhibited SOS induction in lexA+ strains. The effect of pLM109 on the UV sensitivity of lexA(Def) strains was similar to that of the parental umuD+C+ plasmid. The mutation responsible for the phenotypes of pLM109 was localized to a 615-bp fragment. DNA sequencing revealed that the umuC125 mutation was a G:C----A:T transition that changed codon 39 of umuC from GCC----GTC thus changing Ala39 to Val39. The implications of the umuC125 mutation for umuDC-dependent effects on UV-mutagenesis and cell survival after UV damage are discussed.

PubMed ID: 1944335 Exiting the NIEHS site

MeSH Terms: Alleles; Cloning, Molecular; Escherichia coli/genetics*; Escherichia coli/growth & development; Escherichia coli/radiation effects; Genes, Bacterial; Kinetics; Mitomycin/pharmacology; Mutagenesis; Mutation*; Phenotype; Plasmids*; SOS Response (Genetics); Temperature; Ultraviolet Rays

to Top