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PubMed1976

Control of cI gene expression in bacteriophage lambda imm434, studied in an immunity/trp fusion made in vitro.

The trp genes of a lambda imm434 trp-transducing phage have been fused to the immunity region by deletion, in vitro, of the DNA between two targets for the restriction enzyme R.EcoRI. The resulting phage has been used to study the control of expression of the cI gene in vivo. The constitutive rate of expression of the cI gene is between 2 and 5% of the maximally stimulated rate. The products of the cII and cIII genes enhance expression of cI on infection of a sensitive host. The requirement for the cII product is more stringent than that for the cIII protein. The phage 434 repressor present in a 434-immune cell stimulates the rate of cI expression from a superinfecting homoimmune phage about fifteen-fold. This result strongly suggests that repressor stimulates its own synthesis by a direct effect on transcription of the cI gene.

Chromosome Mapping↗
PubMed1976

Efficient suppression of the requirement for N function of bacteriophage lambda by a Rho-defective E.coli suA mutant.

The E. coli suA mutant (T82), which is a suppressor of polarity by virtue of its impaired transcription termination factor (rho) activity, is shown to be an efficient suppressor of lambdaN- mutants. The relief of the N requirement by this host is reflected in a substantial restoration of growth and N-dependent beta-galactosidase expression as well as in a partial relief of polarity of N-defective phages.

Coliphages↗
PubMed1977

Rolling circle replicative structure of bacteriophage lambda DNA in a recombination deficient system.

Rolling-circle replicating structures which represent late stage lambda DNA replication can be detected among intracellular phage lambda DNA molecules under recombination deficient conditions as well as in wild-type infections. Furthermore, if initiation of lambda replication is delayed until the late stage of lambda infection, then nearly all replicating molecules are rolling-circle, even in the first round. Thus neither genetic recombination nor termination of a round of replication are required for generation of rolling-circle replicating molecules of lambda DNA.

Coliphages↗
PubMed1975

Rec-mediated recombinational hot spot activity in bacteriophage lambda. IV. Effect of heterology on Chi-stimulated crossing over.

A Chi mutation in phage lambda stimulates Rec-mediated crossing over more to one side of itself than to the other; stimulation, which is maximal near Chi, can occur at some distance from the Chi site as well. A gross heterology differentiating the two recombining parents does not interfere with the distant Chi-stimulated crossover whether the heterology is at the Chi site or between the Chi site and the distant interval in which recombination is monitored. These conclusions hold whether recombination is measured "genetically" in standard crosses or "physically" in density-labeled crosses conducted in the absence of DNA replication.

Chromosome Mapping↗
PubMed1979

Cloning of the replication gene P of bacteriophage lambda: effects of increased P-protein synthesis on cellular and phage DNA replication.

A restriction fragment of lambdaDNA carrying the P gene was cloned in the high copy number plasmid RSF2124. Cells harbouring this new plasmid RSF2124/lambdaE complement lambdaPam80 phage. A lac promoter-operator region (lacP), produced by EcoRI digestion of plasmid pKB252, was inserted into RSF2124/lambdaE such that induction of the lac promoter by IPTG or lactose leads to increased production of the P gene product. A high amount of P protein in E. coli cells results in a slow inhibition of bacterial DNA synthesis, suggesting that the initiation reaction is blocked by P protein. Synthesis of lambdaDNA proceeds normally under these conditions. Nonsuppressing groPA15 mutant bacteria which are unable to support the replication of wild-type lambda (lambdawt), acquire the ability to replicate lambdaPam80 phage but not lambdawt when they are transformed with a plasmid carrying the lambdaP gene. When harbouring a plasmid containing the mutant Pamber 80 gene, groPA15 mutants are able to support the replication of lambdawt phage when infected at a high multiplicity. lambdaPam80 phage does not multiply in these cells.

Coliphages↗
PubMed1978

Regulation of the int gene of bacteriophage lambda: activation by the cII and cIII gene products and the role of the Pi and Pl promoters.

The activation of the int gene by the cII and cIII gene products was studied by analysing int expression following infection of UV-irradiated cells by various phage mutants. Residual expression of int, probably from Pl, takes place in the absence of cII/cIII activation. Activation of the int gene, like that of the cI repressor gene, is poor at low multiplicities of infection. The mutation intC, which allows constitutive int expression in the lysogenic state, partially relieves the requirement for cII and cIII activation. The kinetics of Int synthesis after addition of the inhibitor rifampicin suggest that the activation occurs at the transcriptional level.

Coliphages↗
PubMed1977

Repressor and int synthesis of bacteriophage lambda in the E. coli host mutant ER437.

Analysis of lambda phage infection of the host mutant ER437 by SDS polyacrylamide gel electrophoresis and autoradiography has revealed altered expression of repressor and integration function (Int). We show that in this host Int as well as repressor synthesis is not dependent upon the lambdacIII gene product in the usual manner, nor is their synthesis turned off in the normal way.

Autoradiography↗
PubMed1976

Analysis of a temperature sensitive mutation in gene cII of bacteriophage lambda.

The mutation cIIts612 was found to map outside the immunity region of phage lambdaimm21 hybrid. As expected of a cII mutation, lambdacIIts612 is unable to stimulate either cI repressor or Int synthesis during the establishment of lysogeny. These results indicate that part of the cII gene of lambda is homologous to that of lambdaimm21 phage.

Coliphages↗