SEARCH · PubMed Health

Results for “Bacteriophage lambda”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources

PubMed1976

Lysogenization of Escherichia coli by bacteriophage Lambda: complementary activity of the host's DNA polymerase I and ligase and bacteriophage replication proteins Q and P.

When bacteriophage lambda DNA replication is blocked by mutation in phage genes O or P, the efficiency of lysogenization drops to a very low value unless high multiplicities of infecting phage are used. Our results show that even at high multiplicity, lambda O or P mutants cannot efficiently lysogenize some hosts that are defective in either DNA polymerase I or DNA ligase. Covalent closure of infecting DNA molecules, a preliminary step for insertion according to Campbell's model and an obvious candidate for this lysogenization defect, appears to occur normally under our conditions. In addition, prophage excision as measured by the frequency of curing O- and P- lysogens seemed normal when tested in the poll- strain. These results suggest that the Escherichia coli enzymes DNA polymerase I and ligase, and phage proteins O and P, are able to provide some complementary activity whose function is required specifically for prophage integration.

Coliphages↗

PubMed1984

Evidence for inclusion of regions of nonhomology in heteroduplex products of bacteriophage lambda recombination.

Total intracellular DNA was isolated from replication-restricted bacteriophage lambda crosses in which the infecting parents were heteroallelic for wild-type and deletion mutant alleles. This DNA was examined for the presence of heteroduplex DNA molecules that contained wild-type sequences in one strand and deletion-mutant sequences in the other. Molecules hybrid for a 689-nucleotide deletion in the immunity region of lambda were detected at significant levels only in crosses in which both the red recombination system of lambda and the rec recombination system of Escherichia coli were active. Molecules hybrid for a 1300-nucleotide deletion in the central portion of the lambda genome were detected at significant levels in DNA isolated from both red+ and red- crosses in which recA function was present.

Bacteriophage lambda↗

PubMed1988

The Nul subunit of bacteriophage lambda terminase binds to specific sites in cos DNA.

The maturation and packaging of bacteriophage lambda DNA are under the control of the multifunctional viral terminase enzyme, which is composed of the protein products of Nu1 and A, the two most leftward genes of the phage chromosome. Terminase binds selectively to the cohesive end site (cos) of multimeric replicating lambda DNA and introduces staggered nicks to regenerate the 12-base single-stranded cohesive ends of the mature phage genome. The purified gpNu1 subunit of terminase forms specific complexes with cos lambda DNA. DNase I footprinting experiments showed that gpNu1 bound to three distinct regions near the extreme left end of the lambda chromosome. These regions coincided with two 16-base-pair sequences (CTGTCGTTTCCTTTCT) that were in inverted orientation, as well as a truncated version of this sequence. Bear et al. (J. Virol. 52:966-972,1984) isolated a mutant phage which contained a CG to TA transition at the 10th position of the rightmost 16-base-pair sequence, and this phage (termed lambda cos 154) exhibits a defect in DNA maturation when it replicates in Escherichia coli which is deficient in integration host factor. Footprinting experiments with cos 154 DNA showed that gpNu1 could not bind to the site which contained the mutation but could protect the other two sites. Since the DNA-packaging specificity of terminase resides in the gpNu1 subunit, these studies suggest that terminase uses these three sites as recognition sequences for specific binding to cos lambda.

Bacteriophage lambda↗

PubMed2004

Initial cos cleavage of bacteriophage lambda concatemers requires proheads and gpFI in vivo.

The development of bacteriophage lambda and double-stranded DNA viruses in general involves the convergence of two separate pathways: DNA replication and head assembly. Clearly, packaging will proceed only if an empty capsid shell, the prohead, is present to receive the DNA, but genetic evidence suggests that proheads play another role in the packaging process. For example, lambda phages with an amber mutation in any head gene or in FI, the gene encoding the accessory packaging protein gpFI, are able to produce normal amounts of DNA concatemers but they are not cut, or matured, into unit length chromosomes for packaging. Similar observations have been made for herpes simplex 1 virus. In the case of lambda, a negative model proposes that in the amber phages, unassembled capsid components are inhibitory to maturation, and a positive model suggests that assembled proheads are required for cutting. We tested the negative model by using a deletion mutant devoid of all prohead genes and FI in an in vivo cos cleavage assay; in this deleted phage, the cohesive ends were not cut. When lambda proheads and gpFI were provided in vivo via a second prophage, cutting was restored, and gpFI was required, results that support the positive model. Phage 21 is a sister phage of lambda, and although its capsid proteins share approximately 60% residue identity with lambda's, phage 21 proheads did not restore cutting, even when provided with the accessory protein gpFI. Models for the role of proheads and gpFI in cos cutting are discussed.

Bacteriophage lambda↗

PubMed1994

Degradation of bacteriophage lambda deoxyribonucleic acid in vitro by sulfur mustard.

The degradation of bacteriophage lambda (lambda) deoxyribonucleic acid (DNA) by interaction with 0.1, 0.5 and 1 mM concentrations of sulfur mustard (SM) was investigated using agarose gel electrophoresis. Alkaline agarose gel electrophoresis also revealed single strand breaks at 0.5 and 0.1 mM concentrations of SM. The presence of magnesium ions in the reaction mixture prevented DNA degradation. It is proposed that the degradation of lambda DNA by its interaction with an excess of SM may be caused by the breakage of phosphodiester backbone of DNA via the formation of an intermediate phosphotriester bond.

Bacteriophage lambda↗

PubMed1983

The bacteriophage lambda O replication protein: isolation and characterization of the amplified initiator.

The bacteriophage lambda O protein participates in the initiation of lambda DNA replication. The lambda O gene was cloned into plasmid pKC30 such that its expression was controlled by the lambda PL promoter. A lambda prophage-coded thermosensitive cI repressor was used to regulate transcription of the cloned O gene. Thermal inactivation of the lambda cI repressor resulted in overproduction of the O protein until it constituted approximately 20% of the total cellular protein of Escherichia coli. A simple three-step purification protocol was developed that yields several milligrams of homogeneous O protein per gram of cell paste. The precise position of the O gene in the known lambda DNA sequence was identified from the amino-terminal sequence of the isolated O protein. Purified O protein stimulated the replication of plasmid lambda dv DNA in vitro and specifically bound to duplex DNA fragments carrying the lambda replication origin.

Amino Acid Sequence↗

PubMed1975

The nucleotide sequence in the promoter region of the gene N in bacteriophage lambda.

The sequence of 18 nucleotides in the region preceding the initiation of transcription of the gene N of bacteriophage lambda has been determined to be as follows (see article). The basic approach used for the sequence determination involved Escherichia coli DNA polymerase I-catalyzed elongation of the octadecanucleotide primer, dT-C-A-G-T-G-C-G-T-C-C-T-G-C-T-G-A-rU, possessing the appropriate polarity and nucleotide sequence corresponding to the 5' end of the gene N transcript. Following hybridization of the primer to the r-stand of bacteriophage lambda CI85657, sequences of the newly grown ollgonucleotide chains were determined by a) partial exonuclease digestion followed by two-dimensional fingerprinting; b) determination of pyrimidine tracts; and c) nearest neighbor analyses. Primer elongation was carried out in a controlled manner, the size of the newly grown chains being kept short by the following techniques: a) insertion of a ribonucleotide unit as the 3' terminus of the primer; b) use of a limited number of deoxynucleoside 5'-triphosphates in the elongation reaction; and c) enlongation of the primer using all the four nucleoside triphosphates with one of the triphosphates being supplied in a limiting concentration.

Base Sequence↗

PubMed1982

Avian myeloblastosis provirus cloned in a lambda bacteriophage is leukemogenic.

The avian myeloblastosis virus provirus inserted in a lambda bacteriophage, recombinant clone 11A1-1 (Souza et al., Proc. Natl. Acad. Sci. U.S.A. 77:3004-3008, 1980), was transfected into chicken embryo fibroblasts which had been preinfected with either Rous-associated virus type 61 or the transformation-defective avian sarcoma virus tdB77. Within 4 to 5 h after transfection, the cells were injected into 16-day-old chicken embryos or 1-day-old chicks. Acute myeloblastic leukemia developed after a long latent period. Filtered (0.22-micrometer pores) supernatant of transformed buffy-coat cell cultures from one leukemic chicken of the lambda 11A1-1 (tdB77) group rapidly transformed yolk sac cells in vitro. Results from an infectivity interference assay and analysis of proviral DNA fragments generated with restriction endonucleases were consistent with the presence in leukemic cells of defective avian myeloblastosis virus and tdB77 as the helper virus.

Animals↗

PubMed1985

Specialized nucleoprotein structures at the origin of replication of bacteriophage lambda: complexes with lambda O protein and with lambda O, lambda P, and Escherichia coli DnaB proteins.

The O protein of bacteriophage lambda is required for initiation of DNA replication at the lambda replicative origin designated ori lambda. The binding sites for O protein are four direct repeats, each of which is an inverted repeat. By means of electron microscopy, we have found that phage lambda O protein utilizes these multiple binding sites to form a specific nucleoprotein structure in which the origin DNA is inferred to be folded or wound. The phage lambda O and P proteins and host DnaB protein interact at ori lambda to generate a larger structure than that formed by O protein alone; P and DnaB proteins fail to form any observable complex when O protein is excluded from the reaction mixture. We conclude that the specialized nucleoprotein structure formed by phage lambda O protein and ori lambda provides for localized initiation of DNA replication by serving as the foundation for the assembly of the initial priming structure. Specialized nucleoprotein structures may be a general means to confer exceptional accuracy on DNA transactions requiring extraordinary precision.

Bacterial Proteins↗

PubMed1981

Recombination of uracil-containing lambda bacteriophages.

Controlled incorporation of uracil into the deoxyribonucleic acid (DNA) of lambda bacteriophages was achieved by growth on dut ung thy mutants of Escherichia coli. The frequency of substitution of uracil for thymine, estimated by alkaline sucrose sedimentation of phage DNA treated in vitro with uracil DNA glycosylase, ranged from 0.17 to 1.9%. The corresponding ratio between the plating efficiencies on wild-type (Ung+) and glycosylase-deficient (Ung-) bacteria ranged from 0.70 to 0.05. If a single-hit dependence of plating efficiency on uracil content is assumed, the probability that any given uracil residue is lethal is approximately 1% (about one-fifth the probability for a pyrimidine dimer). The effect of uracil on recombination was studied in experiments with lambda tandem duplication phages (ethylenediaminetetraacetic acid [EDTA] sensitive), which are converted to single-copy phages (EDTA resistant) by general recombination. For repressed infections (of homoimmune lysogens), recombination was measured by a two-stage assay (DNA extraction, transfection of spheroplasts, and EDTA treatment). The frequencies observed for uracil-containing phages (2 to 4%) were 5 to 10 times higher than control values. However, comparisons with ultraviolet irradiated phages indicated that uracil residues promoted recombination less than 1/100 as efficiently as ultraviolet-induced lesions. Recombination of uracil-containing phages during repressed infections was negligible in recA and partially reduced in recB bacteria. Recombination was very low in ung cells, suggesting that excision repair was responsible for the stimulation. Interestingly, uracil-stimulated recombination was elevated about twofold in xth bacteria.

Bacteriophage lambda↗

PubMed1983

Structure and inherent properties of the bacteriophage lambda head shell. IV. Small-head mutants.

Missense mutants of bacteriophage lambda that produce small proheads were found among prophage mutants defective in the major head protein gpE. Measurements of the sedimentation coefficient and molecular weight of the small proheads showed that they have the T = 4 structure composed of 240 molecules of gpE instead of the wild-type T = 7 structure composed of 420 molecules of gpE. When the phage mutants were grown in groE mutants of Escherichia coli, they produced small unprocessed proheads, which contained a smaller number (about 60) of the core protein (gpNu3) molecules than normal unprocessed proheads, which contain about 180 molecules of gpNu3. This shows that the major head protein determines the size of not only the shell but also the core of unprocessed proheads. These mutants by themselves produce very few mature small-headed phage particles, partly because the lambda DNA molecule, whose cos sites are separated at a distance of 48,500 bases, is too long to be packaged into the small proheads. However, the small proheads can package shorter DNA in vivo and in vitro at somewhat reduced efficiency, if the length or a multiple of the length between the cos sites of the DNA is 13,000 to 19,000 bases.

Bacteriophage lambda↗

PubMed1990

Selection for mutations in the PR promoter of bacteriophage lambda.

Insertion of DNA containing PR, the early rightward promoter of bacteriophage lambda, is lethal to M13-derived vectors when the promoter directs transcription (using the '+' strand as template) toward the M13 origin of replication (ori). Lethality can be relieved by mutation of PR, repression of the promoter by the lambda cl repressor, or by insertion of a strong transcription terminator between PR and ori. We have used selection for plaque formation in the absence of repressor to isolate 14 different mutations at 8 sites in PR. This method of isolating promoter mutants in vivo is applicable generally to strong promoters whose activity is regulated either positively or negatively.

Bacteriophage lambda↗

PubMed1992

Ar+ plasma-induced damage to DNA in bacteriophage lambda: implications for the arrangement of DNA in the phage head.

Bacteriophage lambda was bombarded with low-energy Ar+ ions with the goal of determining whether particular regions of the DNA genome are found preferentially in the outer portion of the packaged DNA mass. The strategy was to fragment the DNA selectively near the surface of the virus by exposing intact phage to Ar+ ions energetic enough to break covalent chemical bonds in DNA but not energetic enough to penetrate deeply beneath the viral capsid shell. Broken DNA was then isolated, and its genomic origin was identified by Southern hybridization to mapped restriction fragments of lambda DNA. Analysis of such Southern blots revealed that all regions of the lambda genome were represented among the small DNA fragments generated during all times of Ar+ bombardment examined. Depending on the duration of exposure, however, particular regions of the genome were found to be enriched in the small-fragment population. After short periods of exposure, sequences from the leftmost 10% and from the right half of the standard genetic map were enriched in the broken-DNA fraction. Among sequences in the right half of the genome, the enrichment was progressively more pronounced beginning in the middle of the genetic map and proceeding toward the right end. In phage bombarded for longer periods of time, rightward sequences were preferentially depleted in the small-fragment population. In contrast, when Ar+ bombardment was carried out with free lambda DNA rather than intact phage, small DNA fragments arose uniformly from all regions of the genome at all times of exposure examined. The results indicate that in the intact phage, DNA sequences from the right half and from the very leftmost regions of the genome have a tendency to lie closer to the capsid than does the remainder of the genome. Since DNA is packaged into the prohead beginning at the left end, our results suggest that packaging occurs in such a way that newly entering DNA tends to be disposed externally to that packaged at earlier times.

Argon↗

PubMed1980

Bacteriophage lambda cloning vehicles for studies of genetic recombination.

A pair of bacteriophage lambda cloning vehicles has been constructed for use in studies of genetic recombination. These phages, lambda rva and lambda rvb, have the following properties: (1) Each vector has a single HindIII site in the immunity region, at which segments of DNA can be inserted. (2) These HindIII sites are flanked by selectable markers with the following phenotypes: Spi+/- (Fec+/-) to the left, and imm lambda or imm434 to the right. (3) There is essentially no sequence homology between the two phages in this region, so recombination of the markers at reasonable frequency depends on the presence of homologous inserts at the HindIII sites. As a consequence, recovered recombinants must have resulted from a crossover event within the insert DNA. Restriction enzyme maps of the vectors have been determined. Variants of the original vectors have been isolated which permit separate examination of the viral (Red) and bacterial (Rec) generalized recombination mechanisms, and which provide a standard interval to which frequencies of recombination in cloned DNAs can be compared.

Bacteriophage lambda↗

PubMed2005

Crystal structure of bacteriophage lambda cII and its DNA complex.

The tetrameric cII protein from bacteriophage lambda activates transcription from the phage promoters P(RE), P(I), and P(AQ) by binding to two direct repeats that flank the promoter -35 element. Here, we present the X-ray crystal structure of cII alone (2.8 A resolution) and in complex with its DNA operator from P(RE) (1.7 A resolution). The structures provide a basis for modeling of the activation complex with the RNA polymerase holoenzyme, and point to the key role for the RNA polymerase alpha subunit C-terminal domain (alphaCTD) in cII-dependent activation, which forms a bridge of protein/protein interactions between cII and the RNA polymerase sigma subunit. The model makes specific predictions for protein/protein interactions between cII and alphaCTD, and between alphaCTD and sigma, which are supported by previous genetic studies.

Bacteriophage lambda↗

PubMed1982

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

The bacteriophage lambda int gene product, integrase, recombines the phage DNA with the host DNA at specific sites on each to accomplish lysogeny. The int gene is transcribed from two promoters, PL and PI, each regulated positively by lambda proteins. The expression of integrase is also controlled from a site, sib, in the b region of the phage genome. This is a unique regulatory site because it is located distal to the structural gene in relation to the promoters. The expression of int from the PL promoter is inhibited when sib is present. This effect appears to be specific for PL because sib does not cause inhibition of PI-dependent int synthesis. lambda mutants that contain alterations in the site have been isolated. Sequence analyses of the mutations reveal single base changes, spanning 37 base pairs (bp) in the b region, some 240 bp beyond the int gene. Another mutant, hef13, which has a phenotype similar to that of sib, introduces a nucleotide change within the same 37-bp region. The sib and hef mutations cluster within a region of dyad symmetry. Regulation of int synthesis by sib occurs after transcription of the int gene. There is no difference in the rate of PL-promoted int mRNA synthesis in either sib+ or sib- phage infections, yet int mRNA is less stable in the sib+ infection. Because RNase III host mutants are defective in sib regulation, processing of the PL mRNA at sib by this endoribonuclease may cause int mRNA decay and decrease int synthesis.

Bacteriophage lambda↗

PubMed1999

Rings and filaments of beta protein from bacteriophage lambda suggest a superfamily of recombination proteins.

The beta protein of bacteriophage lambda acts in homologous genetic recombination by catalyzing the annealing of complementary single-stranded DNA produced by the lambda exonuclease. It has been shown that the beta protein binds to the products of the annealing reaction more tightly than to the initial substrates. We find that beta protein exists in three structural states. In the absence of DNA, beta protein forms inactive rings with approximately 12 subunits. The active form of the beta protein in the presence of oligonucleotides or single-stranded DNA is a ring, composed of approximately 15-18 subunits. The double-stranded products of the annealing reaction catalyzed by the rings are bound by beta protein in a left-handed helical structure, which protects the products from nucleolytic degradation. These observations suggest structural homology for a family of proteins, including the phage P22 erf, the bacterial RecT, and the eukaryotic Rad52 proteins, all of which are involved in homologous recombination.

Bacteriophage lambda↗

PubMed1993

Molecular epidemiology of Escherichia coli O157:H7 strains by bacteriophage lambda restriction fragment length polymorphism analysis: application to a multistate foodborne outbreak and a day-care center cluster.

Genomic DNAs prepared from 168 isolates of Escherichia coli O157:H7 were analyzed for restriction fragment length polymorphisms on Southern blots probed with bacteriophage lambda DNA. The isolates analyzed included strains from a recent large multistate outbreak of E. coli O157:H7 infection associated with consumption of poorly cooked beef in restaurants, a day-care center cluster, and temporally and geographically unrelated isolates. E. coli O157:H7 isolates recovered from the incriminated meat and from 61 (96.8%) of 63 patients from Washington and Nevada possessed identical lambda restriction fragment length patterns. The lambda restriction fragment length polymorphisms observed in 11 (91.7%) of 12 day-care center patients were identical, but they differed from that of the strain associated with the multistate outbreak. E. coli O157:H7 from 42 patients temporally or geographically unrelated to either cluster of infection possessed unique and different lambda restriction fragment length patterns, except for paired isolates from three separate clusters of infection. These data demonstrate that the hybridization of DNA digests of E. coli O157:H7 with radiolabelled bacteriophage lambda DNA can be a useful, stable, and discriminatory epidemiologic tool for analyzing the linkage between strains of E. coli O157:H7.

Animals↗