title: Properties of bacteriophage T4 proteins deficient in replication repair.
abstract: An epistasis group of mutations engendering increased sensitivity to diverse DNA-damaging agents was described previously in bacteriophage T4. These mutations are alleles of genes 32 and 41, which, respectively, encode a single-stranded DNA-binding protein (gp32) and the replicative DNA helicase (gp41). The mechanism by which the lethality of DNA damage is mitigated is unknown but seems not to involve the direct reversal of damage, excision repair, conventional recombination repair, or translesion synthesis. Here we explore the hypothesis that the mechanism involves a switch in DNA primer extension from the cognate template to an alternative template, the just-synthesized daughter strand of the other parental strand. The activities of the mutant proteins are reduced about 2-fold (for gp32) or 4-fold (for gp41) in replication complexes catalyzing coordinated synthesis of leading and lagging strands, in binding single-stranded DNA, promoting DNA annealing, and promoting branch migration. In striking contrast, the mutant proteins are strongly impaired in promoting template switching, thus supporting the hypothesis of survival by template switching.
authors.affiliation: Laboratory of Molecular Genetics, NIEHS, National Institutes of Health/Department of Health and Human Services, Research Triangle Park, North Carolina 27709-2233, USA.
authors.forename: Farid A
authors.initials: FA
authors.lastname: Kadyrov
authors.forename: John W
authors.initials: JW
authors.lastname: Drake
mesh_terms: D017122:Bacteriophage T4 / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004260:DNA Repair; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; D014764:Viral Proteins; C063983:gene 41 protein, Enterobacteria phage T4; C060035:gp32 protein, Enterobacteria phage T4