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Biomedical subjects

I A Bass

Publications and source records attributed to I A Bass.

31 records · Page 2Linked to original sources
PubMed1979

The effect of rifampicin upon the transcription of RNA polymerase beta-gene in Escherichia coli.

We studied the rate of synthesis of beta-and beta'-subunits of DNA-dependent RNA polymerase and the rate of beta-polypeptide mRNA synthesis in rifampicin-treated bacteria. The chosen antibiotic doses did not significantly inhibit the total RNA and protein synthesis in rifampicin-sensitive bacteria. For RNA-DNA hybridization experiments a pOD162 plasmid was constructed carrying a fragment of the rpoB gene and no other chromosome DNA regions. It was found that low doses of rifampicin cause an absolute and a relative increase in the rate of synthesis of the specific mRNA for the beta-subunit, suggesting a stimulation of the corresponding gene transcription and excluding the possibility of a less pronounced inhibition of the rpoB gene expression compared to that of most other genes. However the relative acceleration of transcription is substantially higher than the absolute one. The stimulating effect of rifampicin on the beta-polypeptide synthesis is also demonstrated in a coupled system of transcription and translation directed by lambda rifd47 DNA. The possible mechanisms of the rifampicin action are discussed.

DNA-Directed RNA Polymerases↗
PubMedDate not supplied

[Horizontal transfer of mercury resistance genes in natural bacterial populations].

The results of studying the horizontal transfer of mercury resistance determinants in environmental bacterial populations are reviewed. Identical or highly homologous mercury resistance (mer) operons and transposons were found in bacteria of different taxonomic groups from geographically distant regions. Recombinant mer operons and transposons were revealed. The data suggest high frequencies of horizontal transfer and of recombination for mercury resistance determinants. The mechanisms of horizontal gene transfer were elucidated in Gram-negative and Gram-positive bacteria. New transposons were found and analyzed.

Bacteria↗
PubMedDate not supplied

[The region of phage T4 W-29 genes: cloning and expression].

The EcoRI fragment of T4 DNA containing the W-29 genes and its subfragments were cloned in the pBR322 and the singlestranded M13 phage. Hybridization with a cloned DNA showed that in T4 infected cells the transcription of the late genes 25-29 depends on the phage-induced RNA polymerase changes and on replication of phage DNA. At a late infection stage one also observes an enhanced transcription of the (early) genes uvsW and uvsY, which depends on viral DNA replication. Both early and late genes within recombinant plasmids are also expressed in uninfected cells carrying a plasmid regardless of the inserted fragment orientation and independently of the vector promoters. Hybrid plasmids demonstrated a high frequency of recombination with phage DNA in the infected cell. An RNA polymerase from uninfected cells binds itself to the late cloned genes to form "open" complexes. A purified RNA polymerase transcribes both early and late genes within recombinant plasmids. The relative transcription of the late cloned genes is enhanced if one uses an RNA polymerase from T4-infected cells. The super-helicity of template DNA is essential for transcription of early and late genes.

Chromosome Mapping↗
PubMedDate not supplied

[Similar organization of beta,beta'-subunit RNA-polymerase genes and adjacent ribosomal protein genes in Enterobacteriaceae and Pseudomonas putida].

The genes coding for the RNA-polymerase beta,beta'-subunits and adjacent ribosomal protein genes in Escherichia coli, Salmonella typhimurium, Shigella flexneri, Serratia marcescens, Proteus mirabilis and Pseudomonas putida are compared by the Southern hybridization procedure. In all the species studied close clustering of the genes rplKAJL and rpoBC is demonstrated. Preliminary physical maps for these genes in S. typhimurium, S. flexneri, S. marcescens and P. mirabilis are proposed. Rifampicin is shown to stimulate the beta,beta'-subunit synthesis in all the species studied, suggesting the existence of attenuators localized in front of the rpoBC genes. The similar arrangement of the genes rplKAJLrpoBC in a number of bacterial species is proposed to be due to common mechanisms of their coordinate expression.

Base Sequence↗
PubMedDate not supplied

[Effect of several factors on synthesis of RNA-polymerase subunits by Escherichia coli K12].

In merodiploid cells containing a double dose of structural genes of RNA polymerase subunits--rpoB and rpoC--the rate of synthesis of beta- and beta'-subunits is 2 times higher than in haploid cells. Missense mutation rpoC1 (tsX) in the beta'-polypeptide gene accelerates the synthesis of both beta- and beta'-subunits, particularly at a nonpermissive temperature. When rpoB-rpoC operon containing mutation rpoC1 is duplicated no dose effect of these genes is observed. In the heterozygous state mutation rpoC1 produces almost no accelerating effect on the synthesis of RNA polymerase subunits i. e. is recessive with respect to the wild allele of rpoC. In the presence of rifampicin the synthesis of RNA polymerase subunits in a sensitive wild-type strain is stimulated 6-fold, the same effect is observed with cells carrying mutation rpoC1, the latter, however, itself accelerates the synthesis of these subunits 3-fold. Thus the effects of rifampicin and the mutation are synergistic indicating that these factors act independently. Similar data have also been obtained with rifampicin-treated cells of rpoB22 amber-mutant. In UV-irradiated cells, amino acid incorporation into beta- and beta'-subunits declines more rapidly than into the total protein. When either irradiated or non-irradiated cells are infected with a transducing phage lambdarifd-47 which carries rpoB gene, the synthesis of beta-proceeds at a higher rate. Irradiation of bacteria before the infection (500 erg/mm2) results in 6.5-fold acceleration of the synthesis induced by subsequent infection with lambdarifd-47 as compared to non-infected non-irradiated cells; the fraction of newly formed beta-polypeptide with respect to total protein grows 20-fold in this case. The data are considered with regard to the possible mechanisms of regulation of synthesis of RNA polymerase subunits.

Bacterial Proteins↗
PubMedDate not supplied

[Effect of rifampicin on the synthesis of bacterial RNA polymerase mRNA by means of hybrid plasmids].

We studied the rate of synthesis of beta- and beta'-subunits of DNA-dependent RNA polymerase and the rate of beta-polypeptide mRNA synthesis in rifampicin-treated bacteria. The antibiotic doses used did not significantly inhibit the total RNA and protein synthesis in rifampicin-sensitive bacteria. For RNA-DNA hybridization experiments a pOD162 plasmid was constructed carrying a fragment of the rpoB gene and no other chromosome DNA regions. It is found that low doses of rifampicin cause an absolute and differential increase in the rate of synthesis of the specific mRNA for the beta-subunit, suggesting a stimulation of the corresponding gene transcription. However the absolute transcription stimulation does not fully correlate with the relative acceleration of beta-mRNA and the corresponding polypeptide synthesis. The stimulating effect of rifampicin on the beta-polypeptide synthesis was demonstrated also in a coupled system of transcription and translation directed by lambda rifd 47 DNA. The possible mechanisms of the rifampicin action are discussed.

DNA-Directed RNA Polymerases↗
PubMedDate not supplied

[Cloning of the promoter of the RNA polymerase operon located before the structural gene of the beta-subunit].

An EcoRI-fragment of the rpoBC operon carrying the end of the rplL gene, the intercistron region and the beginning of the rpoB gene cloned on the pBRH4 plasmid makes it tetracyclin-resistant, i. e. possesses the properties of a promoter. There is no appreciable difference in the degree of antibiotic resistance of recombinant plasmids carrying the main PJ promoter and the additional promoter.

Cloning, Molecular↗