title: Genetic and molecular characteristics of X-ray-sensitive mutants of Escherichia coli defective in repair synthesis.
abstract: Alleles responsible for X-ray-sensitive characteristics of three mutants of Escherichia coli B, which were also sensitive to ultraviolet (UV) irradiation, were mapped near metE locus, and named res-1, res-2, and res-3. All the res(-) mutants showed no host cell reactivability (Hcr(-)) for transducing deoxyribonucleic acid (DNA) of P1 phage irradiated by UV but they were Hcr(+) for infective DNA of P1 phage. Furthermore, they showed no detectable activity of DNA polymerase. Characteristics of allele res-1 were studied in detail. The mutant res-1 uvr(+) showed an extensive degradation of DNA after UV irradiation. Double mutants carrying res-1 uvrA(-), res-1 uvrB(-), and res-1 uvrC(-) showed no marked increase in UV sensitivity beyond that of the uvr(-) single mutants and only negligible UV-induced DNA degradation. The uvr(-) mutations showed no such suppressive effect on DNA degradation induced by X rays in these double mutants. It is concluded that res(-) mutants are defective in the second step (repair synthesis) of the excision repair process and that DNA polymerase is partly responsible for the assumed resynthesis step.
mesh_terms: D000483:Alleles; D002499:Centrifugation, Density Gradient; D002874:Chromosome Mapping; D003090:Coliphages / Q000528:radiation effects; D003433:Crosses, Genetic; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology / Q000528:radiation effects*; D005796:Genes; D005827:Genetics, Microbial; D009154:Mutation; D009711:Nucleotides / Q000378:metabolism; D011830:Radiation Effects; D013395:Sucrose; D014161:Transduction, Genetic; D014316:Tritium; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D009711:Nucleotides; D014316:Tritium; D013395:Sucrose; D004254:DNA Nucleotidyltransferases