title: Escherichia coli mfd mutant deficient in "mutation frequency decline" lacks strand-specific repair: in vitro complementation with purified coupling factor.
abstract: Mutation frequency decline (MFD) is the rapid decrease in the frequency of certain induced nonsense suppressor mutations occurring when protein synthesis is transiently inhibited immediately after irradiation. MFD is abolished by mutations in the uvrA, -B, or -C genes, which prevent excision repair, or by a mfd mutation, which reduces the rate of excision but does not affect survival. Using an in vitro repair synthesis assay we found that although wild-type cells repair the transcribed (template) strand preferentially, mfd- cells are incapable of strand-specific repair. The deficiency in strand-selective repair of mfd- cell extract was corrected by adding highly purified "transcription-repair coupling factor" to the reaction mixture. We conclude that mfd is, most likely, the gene encoding the transcription-repair coupling factor.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599.
authors.forename: C P
authors.initials: CP
authors.lastname: Selby
authors.forename: E M
authors.initials: EM
authors.lastname: Witkin
authors.forename: A
authors.initials: A
authors.lastname: Sancar
mesh_terms: D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002474:Cell-Free System; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D005816:Genetic Complementation Test; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D010957:Plasmids; D013014:SOS Response, Genetics; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors; C072103:transcription repair coupling factor protein, Bacteria