Characterization of an Escherichia coli Mutant (radB101) Sensitive to γ and uv Radiation, and Methyl Methanesulfonate

Abstract

After N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis of Escherichia coli K-12 (xthA14), and X-ray-sensitive mutant was isolated. This sensitivity is due to a mutation, radB101, which is located at 56.5 min on the E. coli K-12 linkage map. The radB101 mutation sensitized wildtype cells to gamma and uv radiation, and to methyl methanesulfonate. When known DNA repair-deficient mutants were ranked for their gamma-radiation sensitivity relative to their uv-radiation sensitivity, their order was (starting with the most selectively gamma-radiation-sensitive strain): recB21, radB101, wild type, polA1, recF143, lexA101, recA56, uvrD3, and uvrA6. The radB mutant was normal for gamma- and uv-radiation mutagenesis, it showed only a slight enhancement of gamma- and uv-radiation-induced DNA degradation, and it was approximately 60% deficient in recombination ability. The radB gene is suggested to play a role in the recA gene-dependent (Type III) repair of DNA single-strand breaks after gamma irradiation and in postreplication repair after uv irradiation for the following reasons; the radB strain was normal for the host-cell reactivation of gamma- and uv-irradiated bacteriophage lambda; the radB mutation did not sensitize a recA strain, but did sensitize a polA strain to gamma and uv radiation; the radB mutation sensitized a uvrB strain to uv radiation.

Interchromosomal recombination in the extremely radioresistant bacterium Deinococcus radiodurans

“…Previous studies, aimed at determining how such nonspecific DSBs are processed, were restricted to organisms relatively sensitive to irradiation, such as E. coli (32) and S. cerevisiae (30), and were thus limited to the analysis of individual recombinants arising from a few DSB events. This constraint no longer exists now that D. radiodurans populations recovering from 500 DSBs per cell can be studied in mass culture.…”

Roles of therecJandrecNGenes in Homologous Recombination and DNA Repair Pathways ofNeisseria gonorrhoeae

“…The RecN protein has been assigned to the RecF pathway of E. coli based on a 20-to 30-fold induction of recN in recBC sbcBC strains (38). However, the RecN protein is also required for RecBCD-dependent repair of double-strand breaks which arise as a result of DNA damage (37,41,43,62). Additionally, in contrast to the other genes of the RecF pathway, mutations in recN do not restore resistance of E. coli to the absence of thymine known as "thymineless death" (36).…”

Genetic and phenotypic analyses indicating occurrence of the recN262 and radB101 mutations at the same locus in Escherichia coli

“…This mutation maps at 56.5 min (14) relative to the 1983 version of the genetic map for E. coli K-12 (1), and it sensitizes cells to both gamma and UV radiation and to treatment with the alkylating agent methyl methanesulfonate (14). The radB mutant is normal for gamma and UV radiation mutagenesis, it shows only a slight enhancement of gamma and UV radiation-induced DNA degradation, and it shows a 60% deficiency in recombination ability (14).…”

“…This mutation maps at 56.5 min (14) relative to the 1983 version of the genetic map for E. coli K-12 (1), and it sensitizes cells to both gamma and UV radiation and to treatment with the alkylating agent methyl methanesulfonate (14). The radB mutant is normal for gamma and UV radiation mutagenesis, it shows only a slight enhancement of gamma and UV radiation-induced DNA degradation, and it shows a 60% deficiency in recombination ability (14). For gamma or UV radiation-induced killing, the radB mutation does not sensitize a recA strain, but does sensitize a polA strain and a uvrB (UV radiation only) strain, which suggests that the radB gene functions in the "recA epistasis group" for the repair of damaged DNA (14).…”

“…The radB101 mutation was isolated on the basis of its sensitization of Escherichia coli K-12 cells to gamma radiation (14). This mutation maps at 56.5 min (14) relative to the 1983 version of the genetic map for E. coli K-12 (1), and it sensitizes cells to both gamma and UV radiation and to treatment with the alkylating agent methyl methanesulfonate (14).…”