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J A Wechsler

Publications and source records attributed to J A Wechsler.

At least 19 recordsLinked to original sources
PubMed1983

RNA polymerase interaction with dnaB protein and lambda P protein during lambda replication.

The Escherichia coli GroP- phenotype, associated with some dnaB mutants and measured as a decreased ability to plate lambda bacteriophage, was altered by some rpoB mutations. The rpoB effect showed an allele specificity. The participation both of dnaB and of lambda P alleles in the GroP- phenotype was also allele specific. It was concluded that RNA polymerase, dnaB protein, and lambda P protein form a functional complex required for lambda replication.

Alleles↗
PubMed1981

Initiation of chromosomal DNA synthesis in vitro.

An in vitro complementation assay for initiation of chromosomal DNA replication is described. The initiation reaction is dependent upon extract from either of two hybrid-plasmid containing strains. Each hybrid plasmid carries a suppressor of dna A-ts mutations. The in vitro DNA synthesis is heavily biased toward the origin region, and the origin of replication (oriC) is replicated as determined by DNA-DNA hybridizations.

Chromosomes, Bacterial↗
PubMed1981

Complementation of a dnaC initiation defect in vitro.

The dnaC28 mutant, CT28-3b, is an initiation defective dnaC strain. Extracts of the mutant failed to synthesize DNA in vitro when the strain was incubated at the restrictive temperature for two generation times prior to preparation of the extract. Addition of a complementing extract from a Col-E1::dnaC+ hybrid plasmid containing strain or of partially purified dnaC protein resulted in substantial synthesis. Hybridization of the DNA made by these in vitro complementation extracts showed that a significant portion of this DNA was from the region near the chromosomal origin of replication.

Bacteriophage lambda↗
PubMed1981

RNA polymerase is required for DNA initiation in vitro.

We have previously reported in vitro complementation assays for chromosome initiation that enable dnaA and dnaC mutant extracts to synthesize DNA. To examine the role of RNA polymerase in chromosome initiation, inhibitors of the enzyme and anti-RNA polymerase antibody were used. Though rifampicin failed to efficiently inhibit ribonucleoside triphosphate polymerization under the assay conditions, both streptolydigin and anti-RNA polymerase antibody abolished ribonucleic acid synthesis completely. Antibody effectively inhibited chromosome initiation in the dnaA mutant based reaction but streptolydigin did not. Neither streptolydigin nor antibody affected the dnaC-dependent assay. It was concluded that RNA polymerase is required for initiation but not necessarily to polymerize a polyribonucleotide. A scheme for the sequence of initiation events is presented.

Aminoglycosides↗
PubMed1981

DNA replication intermediates synthesized by lysates of dnaB, dnaG and dnaB dnaG mutants in vitro.

Isogenic dnaB, dnaG, and dnaB dnaG mutants were constructed and used as extracts in the cellophane-disc in vitro DNA replication system. The increased proportion of 5S DNA characteristics of the dnab extract and the lack of Okazaki piece synthesis characteristic of the dnaG extract were both apparent in analysis of the dnaB dnaG mutant extract reaction. A hypothetical scheme to explain these results and those of others is presented.

Bacterial Proteins↗
PubMed1981

The isolation and characterization of escherichia coli dnaB::Tn10 insertion mutations.

Exploitation of the ability of the ban protein encoded by phage P1 to compensate for dnaB-defective host mutations, allowed the isolation of dnaB::Tn10 insertion mutations. The presence of P1bac prophage was required for survival of dnaB::Tn10 mutants, and such lysogens were cryosensitive. The insertions were shown to map in dnaB by transduction and this was confirmed by complementation analysis. The dnaB::Tn10 (P1bac) strains were non-permissive for lambda growth but did support the growth of lambda-dnaB+ specialized transducing phage. No antigenically active dnaB product could be detected by immunologic assays using either of two methods. In addition, it was shown that the observe cryosensitivity of P1bac suppression was a direct result of reversible inactivation of the ban protein at low temperature.

Bacterial Proteins↗
PubMed1981

High frequency of genetic duplications in the dnaB region of the Escherichia coli K12 chromosome.

The region that includes the dnaB locus on the E. coli K12 chromosome was shown to be duplicated at high frequency in cell populations. The duplications were shown to be arranged in tandem and segregated at various frequencies. Segregation was dependent on the recA recombination system, but independent of recB,C. Though most of the data was obtained with dnaB::Tn10 insertion mutants, the duplications were shown to occur in the absence of Tn10.

DNA Replication↗
PubMed1981

Isolation and analysis of multicopy extragenic suppressors of dnaA mutations.

Recombinant plasmids were constructed from restriction enzyme digests of Escherichia coli chromosomal deoxyribonucleic acid and pMB9 plasmid deoxyribonucleic acid and selected for correction of the dnaA phenotype. The three plasmids isolated, all retransformed dnaA cells, both recA+ and recA, such that all tetracycline-resistant transformants selected at permissive temperature simultaneously became temperature resistant. Restriction enzyme mapping of the plasmids showed all three to be different, and it was subsequently shown that none contained the dnaA+ gene. Though each of the three plasmids suppressed three different temperature-sensitive dnaA alleles, none corrected the phenotype of an unsuppressed dnaA amber allele. It was concluded, therefore, that each plasmid contained a unique extragenic suppressor of dnaA and that the suppression was observed because of the elevated gene dosage of the cloned material. The plasmids were unstable in the absence of selection.

DNA Replication↗
PubMed1981

Suppression of dnaC alleles by the dnaB analog (ban protein) of bacteriophage P1.

The dnaB analog protein produced by the ban gene of bacteriophage P1 was shown to suppress several Escherichia coli dnaC alleles. Suppression of dnaC7 temperature sensitivity in P1 lysogens of a dnaC7 mutant was complete at all temperatures. For the dnaC2 and dnaC28 alleles, suppression was observed only at intermediate temperatures. Though these intermediate temperatures were sufficient to completely restrict the mutants, at higher temperatures the suppression was not observed. No suppression of the dnaC1 allele was detected. These results have implications concerning the requirement for the dnaB-dnaC complex at the various stages of deoxyribonucleic acid replication.

Alleles↗
PubMed1981

Deoxyribonucleic acid initiation mutation dnaB252 is suppressed by elevated dnaC+ gene dosage.

The Escherichia coli dnaB252 allele is the only dnaB mutation which confers a deoxyribonucleic acid initiation-defective phenotype on the cell. The presence of a multicopy hybrid plasmid containing the dnaC+ gene in a dnaB252 strain completely suppressed the temperature-sensitive phenotype. It is suggested that at high temperature the dnaB252 protein has a lowered affinity for dnaC protein, and that the formation of a dnaB-dnaC complex is mandatory for initiation.

DNA Replication↗
PubMed1981

dnaB125, a dnaB nonsense mutation.

A temperature-sensitive dnaB mutation, dnaB125, was shown to be a suppressed amber mutation. The effects of inserting different amino acids at the mutated site via amber suppressors were examined for both Escherichia coli and bacteriophage gamma growth. In addition, the dnaB125 amber allele was shown to be different from the previously described dnaB amber allele, dnaB266. The extent of residual deoxyribonucleic acid synthesis observed in a supF(Ts) dnaB125 strain at high temperature revealed that the dnaB protein was present in excess and that deoxyribonucleic acid synthesis could continue for several generation equivalents without further production of dnaB protein.

Alleles↗
PubMed1980

dnaA alleles are recessive.

Dominance tests of several dnaA alleles from Escherichia coli, including two previously reported to be dominant, show that all of the mutant alleles examined are recessive to dnaA+.

Alleles↗
PubMed1979

Characterization of arithmetic deoxyribonucleic acid synthesis at restrictive temperature in a dnaE mutant of Escherichia coli K-12.

The dna-293 mutation is shown to be a dnaE allele. The linear deoxyribonucleic acid synthesis previously observed in this mutant has been further characterized. The production of small deoxyribonucleic acid intermediates and their subsequent joining were identical in the mutant and its dnaE+ parent at 42.5 degrees C. Though the mutant cells continued to divide at the nonpermissive temperature, the rate of division was reduced. The data are consistent with a lack of production of replicationally active deoxyribonucleic acid polymerase III at the restrictive temperature.

DNA Polymerase III↗
PubMed1977

Dominance of dnaA+ to dnaA in Escherichia coli.

The dominance of dnaA+ to the dnaA508 mutation was complete and was unaffected by the presence of a copy of the chromosomal replication origin on the episome. These results prove that the dnaA gene of Escherichia coli produces a diffusible product.

Alleles↗