Shin-ichi Tokuno

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A Polymyxin B-sensitive mutant of Salmonella typhimurium (Pox-1) channels all infecting wild-type P22 toward lysogenization. The efficiency of this channeling is sufficiently high that P22c+ (wild type) cannot form plaques on Pox-1; phage mutants defective in repressor synthesis (P22c1, c2, c3) or refractory toward repressor (P22vir B) can form plaques. The(More)
A rifampin-resistant mutant of Salmonella typhimurium carries an altered RNA polymerase. Wild-type (c+) phage P22 displays clear plaques and a reduced lysogenization frequency on this mutant host. The cly mutants of P22 were isolated on the basis of their ability to lysogenize such mutant hosts. Two classes of regulatory events, both of which are dependent(More)
The product of phage P22 gene c1 has two functions: it promotes synthesis of P22 repressor and it retards expression of some lytic genes. We present evidence that this product is inactivated in UV-irradiated hosts. The conditions for inactivation of c1 product include a functional DNA recombination system involving the host recA gene.
Mutants of P22 which have been located in the c2 repressor gene were examined. The most rightward “c2 mutation” was found to define a site that is neccessary only for the establishment and not for the maintenance of repressor synthesis. We concluded that this site c27 is an analog of cy mutants in phage λ which define a promotor for repression establishment(More)
A slowly growing, polymyxin-sensitive mutant of Salmonella typhimurium was isolated. Wild-type phage P22 form plaques on the mutant at 5 x 10(-4), the frequency observed on wild-type hosts. All P22 clear mutants form plaques with near normal frequency. The inability of the mutant to form plaques is correlated with an increase in lysogenization frequency.(More)
The product of phage P22 gene c1 has two functions: (1) it promotes synthesis of repressor and (2) during the first minutes of infection it retards expression of some lytic genes. We call the second, negative function “c1 retardation”. We investigated c1 retardation in a mutant host of Salmonella typhimurium that is resistant to rifampicin and carries an(More)
Phage P22 mutationc27 defines a site required for establishment, but not maintenance of repressor synthesis. This study confirms that P22c27 is able to synthesize repressor if active repressor is present. An interaction involving gene products ofc1 andc3 and the sitec27 retards expression of the lytic genes of P22. Mutations in genec1 eliminate the(More)
The role of DNA repair in transformation was investigated by infecting repair-deficient xeroderma pigmentosum (XP) variant cells, XP variant heterozygous cells, and normal human fibroblasts with simian virus 40 which had been irradiated by ultraviolet light. The transformation frequencies obtained were compared to those observed for unirradiated virus.(More)
A temperature-sensitive simian virus 40 (SV40) mutant, tsTNG-1, has been isolated from nitrosoguanidine-treated and SV40-infected African green monkey kidney (CV-1) cultures. Replication of virus at the nonpermissive temperature (38.7 C) was 3,000-fold less than at the permissive temperature (33.5 C). Plaque formation by SV40tsTNG-1 deoxyribonucleic acid(More)