Lambda phage

About: Lambda phage is a research topic. Over the lifetime, 1609 publications have been published within this topic receiving 84675 citations. The topic is also known as: Enterobacteria phage lambda.

In vitro regulation of phage lambda cII gene expression by Escherichia coli integration host factor

Abstract: The effect of Escherichia coli integration host factor (IHF) on phage lambda gene expression has been examined in a simplified DNA-directed in vitro system that measures the formation of the first dipeptide of the gene product. Plasmid pKC30cII, which contains the phage lambda genes N, cII and O, under control of the PL promoter, was used as template to study the expression of the first dipeptide of the gene products--i.e., fMet-Asp for N protein, fMet-Val for cII, and fMet-Thr for O. Purified IHF stimulates the DNA-directed synthesis of fMet-Val (cII) and fMet-Thr (O) 2-3-fold but has no effect on the synthesis of fMet-Asp (N). In this in vitro system, the stimulation by IHF of cII and O gene expression is at the level of transcription. Phage lambda repressor completely inhibits dipeptide synthesis in the presence or absence of IHF. The results are consistent with a role of IHF as a transcription antiterminator, perhaps functioning at or near the tR1 site preceding the cII gene.

Mutational analysis of a regulatory region in bacteriophage lambda that has overlapping signals for the initiation of transcription and translation

Abstract: The positively regulated PRE promoter of phage lambda structurally overlaps with the ribosome-binding and NH2-terminal coding region of the regulatory protein (cII) that activates PRE transcription. We have isolated and characterized 27 different point mutations that occur within the 36-base-pair overlapping region. A comparison of genetic crossover data with nucleotide separations as determined by DNA sequence analysis reveals that recombination frequencies are greatly depressed at very short distances. Moreover, recombination frequency is critically dependent upon the precise nucleotide sequence of the crossover region for distances of five nucleotides or less. The mutations define precise positions and sequences that are important to (i) PRE promoter function, (ii) translation of the cII gene, and (iii) cII gene function. Mutational changes that affect the function of one element in this region concomitantly define phenotypically silent alterations in the other two elements. Mutations deficient in promoter function (P-RE or cy) are clustered in two regions that lie approximately equal to 10 and approximately equal to 35 nucleotides before the initial base of PRE mRNA, analogous to mutations in other promoters. P-RE mutations in the -10 region alter bases that are conserved in prokaryotic promoters, but P-RE mutations in the -35 region do not affect bases that are normally conserved in other promoters. Several mutations deficient in cII gene activity affect the initiation of cII protein synthesis, including an A leads to G change four bases outside the cII coding region, and AUG leads to GUG, AUG leads to ACG, and AUG leads to AUA mutations in the initiation codon. In the region of overlap between the PRE promoter and the NH2-terminal region of the cII gene, most amino acid substitutions in the cII protein do not result in a loss of cII function, indicating that this region of the gene does not contain essential information for cII function. We suggest that the overlap itself is an evolutionarily conserved structure and that it somehow coordinates the bidirectional transcriptional and translational events that occur in this region.

Construction and propagation of a defective simian virus 40 genome bearing an operator from bacteriophage lambda.

Abstract: A 2400 base pair DNA segment containing the leftward operator (OL) of phage lambda was covalently joined in vitro to a fragment of simian virus 40 (SV40) DNA harboring the SV40 replication origin. The recombinant molecule was propagated in the presence of helper wild-type SV40 DNA in monkey kidney cells and partially cloned by an infectious center procedure. After propagation in monkey cells and purification, the hybrid DNA could be distinguished from wild-type SV40 DNA by its shortened length (about 80% that of SV40), specific hybridization to denatured lambda DNA immobilized on filters, specific affinity for lambda repressor, and preservation of a large part (about 2300 base pairs) of the lambda immunity region as determined by restriction nuclease cleavage patterns and electron microscopic heteroduplex analysis. These results indicate that defective SV40 replicons can serve as vectors for propagating foreign DNA in mammalian cells.

Effect of the direction of DNA replication on mutagenesis by N-methyl-N'-nitro-N-nitrosoguanidine in adapted cells of Escherichia coli.

Abstract: The methylating agent N-methyl-N′-nitro-N-nitrosoguanidine preferentially induces G:C to A:T transitions at DNA base pairs with the G in one particular strand of the cI gene in a lambda prophage, in this case the non-transcribed straind, in Escherichia coli cells in which the adaptive response is induced. The same preference is found for the cI gene inserted in the genome in the inverse orientation, so the differential effect is not caused by the direction of motion of the DNA replicating fork.

The old exonuclease of bacteriophage P2.

Abstract: The Old protein of bacteriophage P2 is responsible for interference with the growth of phage lambda and for killing of recBC mutant Escherichia coli. We have purified Old fused to the maltose-binding protein to 95% purity and characterized its enzymatic properties. The Old protein fused to maltose-binding protein has exonuclease activity on double-stranded DNA as well as nuclease activity on single-stranded DNA and RNA. The direction of digestion of double-stranded DNA is from 5' to 3', and digestion initiates at either the 5'-phosphoryl or 5'-hydroxyl terminus. The nuclease is active on nicked circular DNA, degrades DNA in a processive manner, and releases 5'-phosphoryl mononucleotides.