RESUMEN
Most of bacterial cells in soil samples taken from a mine at the Khaidarkan mercury-antimony deposit (Kirghiz SSR) proved to contain R-plasmids with determinants of mercury resistance (HgCl2). Plasmids had a high molecular mass (approximately 10(8], though some deviated substantially from this size; at least part of them were transmissible. Many Hgr bacteria also showed an increased resistance to antimony (SbCl3), but no relation could be found between this character and the plasmids. Bacteria from soil samples taken at different distances from the mine were virtually devoid of Hgr plasmids: saturation of bacteria with Hgr factors is maintained by selective pressure action only within regions with high concentration of poison. Hgr plasmids at the Khaidarkan deposit were also found in enteric bacteria isolates from the gut of Mus musculus mice and Bufo viridis toads. Some bacterial plasmids from animals carried, apart from Hgr, antibiotic resistance determinants (Tcr, Cmr, Smr), i.e. were multiple resistance factors. These plasmids often displayed intrinsic instability and lost resistance determinants when conjugationally transferred to some E. coli strains.
Asunto(s)
Antimonio , Enterobacteriaceae/genética , Mercurio , Factores R , Microbiología del Suelo , Animales , Bufonidae , Conjugación Genética , ADN Bacteriano/genética , Kirguistán , Ratones , Minería , PlásmidosRESUMEN
Most bacterial cells (Pseudomonas, Acinetobacter) obtained from the soil at the Khaidarkan mercury and antimony mine (Kirghiz USSR) contain R plasmids with mercury (HgCl2) resistance determinants. The plasmids have a large molecular mass (about 100 MD, though smaller ones also occur), and at least some of them are transmissive. Many of the Hgr bacteria also display an elevated antimony (SbCl3) resistance, though this trait was not shown to be plasmid-dependent. There are practically no Hgr plasmids in bacteria taken from the soil at different distances from the mine: the saturation of bacteria with Hgr plasmids is maintained by selective pressure only in the area with a high enough toxin concentration. In the same mercury and antimony deposit area Hgr plasmids were also found in Escherichia coli isolates from the gut of Mus musculus mice and Bufo viridis toads. At least some of the bacterial plasmids obtained from animals also carry antibiotic-resistance determinants (Tcr, Cmr, Smr). These plasmids are also transmissive. They display internal instability and lose their resistance determinants after a conjugation transfer to other E. coli strains.
Asunto(s)
Acinetobacter/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Mercurio/farmacología , Pseudomonas/efectos de los fármacos , Factores R , Microbiología del Suelo , Acinetobacter/aislamiento & purificación , Animales , Antimonio , Bufonidae/microbiología , Farmacorresistencia Microbiana , Escherichia coli/aislamiento & purificación , Ratones/microbiología , Pseudomonas/aislamiento & purificaciónRESUMEN
Five recombinant plasmids, pBK2646, pBK611, pRC3, pRC4 and pRC5, carrying rpoB rifampicin-resistant RNA-polymerase genes were obtained. The sequence analysis of these plasmids revealed certain structural changes in the rpoB gene which specify corresponding alterations in the beta-subunit of RNA polymerase. Some functional properties of the corresponding mutant strains and their RNA polymerases have been investigated.
Asunto(s)
ARN Polimerasas Dirigidas por ADN/genética , Escherichia coli/genética , ARN Polimerasa I/genética , Rifampin/farmacología , Secuencia de Bases , Farmacorresistencia Microbiana , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Genes Bacterianos , Genes Dominantes , Mutación , PlásmidosRESUMEN
The amount of histone structural genes was determined in heterozygotes for two different deficiencies of the histone locus of the 2nd chromosome. In case one chromosome lacks histone genes, the number of histone structural genes in the normal homologous chromosome is likely to increase by means of magnification and compensation in the same way as in the case of rRNA genes.
Asunto(s)
Genes , Histonas/genética , Animales , Cromosomas/fisiología , Drosophila melanogaster/genética , Heterocigoto , Histonas/deficienciaRESUMEN
The transducing phage lambda dsupM814 and the plasmid pIB1830 containing the wild-type rpoB gene have been constructed and the primary structure of the gene's central fragment has been established. In contrast with the wild-type, the gene of the rpoB255 mutant, whose primary structure has been published, was found to contain an A.T. leads to T.A. transversion entailing the substitution of a valine residue for the aspartic acid residue (516) of the wild-type beta subunit.
Asunto(s)
ADN Bacteriano/genética , ARN Polimerasas Dirigidas por ADN/genética , Escherichia coli/enzimología , Genes , Mutación , Rifampin/farmacología , Secuencia de Bases , Enzimas de Restricción del ADN , Farmacorresistencia Microbiana , Escherichia coli/genética , Genes/efectos de los fármacos , Plásmidos , Transducción GenéticaRESUMEN
The paper deals with the various manifestations and the role of genome changes, mainly in eukaryotes. I. Hereditary changes: 1) multiplication of genes in animals; 2) multiplication of genes in prokaryotes; 3) microsymbionts, mobile elements and supermutability; 4) extrachromosomal element delta in Drosophila; 5) hybrid dysgenesis in Drosophila; 6) mobile and unstable genes in drosophila; 7) controlling elements in planrs. II. Genome changes as a regulatory factor of genetic activity: 1) immunoglobulin genes; 2) mating types in yeast; 3) the inversion mechanism of switching gene activity in prokaryotes; 4) ribosomal and histone genes; 5) changes of DNA fractions in ontogenesis; 6) regulation of genome changes.
Asunto(s)
Genotipo , Animales , ADN/análisis , Elementos Transponibles de ADN , Drosophila/genética , Regulación de la Expresión Génica , Genes , Variación Genética , Histonas/genética , Hibridación Genética , Inmunoglobulinas/genética , Ratones , Mutación , Virus Oncogénicos/genética , Plantas/genética , Plásmidos , ARN Ribosómico/genética , Secuencias Repetitivas de Ácidos Nucleicos , Levaduras/genéticaRESUMEN
We have determined the number of histone structural genes in D. melanogaster heterozygotes for two different deficiencies of a histone locus in the 2d chromosome. The results indicate a possibility of histone genes increasing in number in the case of their deficiency through magnification and compensation, as has been shown for rRNA genes by other authors.
Asunto(s)
Drosophila melanogaster/genética , Genes , Histonas/genética , Animales , Replicación del ADN , Heterocigoto , Mutación , Hibridación de Ácido Nucleico , ARN/genéticaRESUMEN
The deficiency of the 38B-40 region containing histone genes in one of the 2nd chromosomes of D. melanogaster triploid intersexes increases the template activity of X-chromosomes both in vivo and in vitro without noticeably affecting autosome activity. This deficiency in the heterozygous state inhibits the variegated position effect of the white gene in the T(1;3)Wvco translocation in diploid females and males, but not affect their rate of development. The variegation suppressor Su(var)hg-1 not only suppress the gene position effect in diploid flies, but also increases the template activity of X-chromosomes in triploid intersexes. The results are discussed with respect to the dependence of gene activity on the structure of chromosomes (density of DNP packing).
Asunto(s)
Drosophila melanogaster/genética , Genes , Histonas/genética , Transcripción Genética , Animales , Femenino , Mutación , Ploidias , Cromosoma XAsunto(s)
Drosophila melanogaster/genética , Herencia Extracromosómica , Genes , Recombinación Genética , Animales , Frío , Femenino , Heterocromatina/genética , Masculino , Mosaicismo , FenotipoRESUMEN
The influence of mutations in structural genes of beta and beta subunits of RNA polymerase upon the synthesis of these subunits in E. coli cells have been investigated. An amber-mutation ts22 in the beta subunit gene decreases the intracellular concentration of this subunit and the rate of its synthesis. At the same time the concentration and the rate of beta subunit synthesis is increased. These suggest the compensatory activation of the RNA polymerase operon that takes place under the conditions of shortage of one of the subunits. Reversions as well as more effective suppression of ts22 amber mutation, achieved by streptomycin addition, substitution of su2 by sul, or by specific mutations, result in a rise of beta and drop of beta subunit concentration and synthesis in ts22 mutant. TsX missense-mutation in the beta subunit gene alters the properties of the enzyme increasing, at the same time, the concentration and the rate of synthesis of both beta and beta subunits, particularly at a nonpermissive temperature. This points to an inversely proportional relationship between the rate of synthesis of RNA polymerase subunits and the total intracellular activity of the enzyme. Extra subunits are rapidly degraded in ts22 and tsX mutants. The whole complex of our data and those of others suggest that the regulation of the synthesis of RNA polymerase subunits is accomplished by interaction of a negative and a positive mechanisms of regulation which include not only activators and repressors but the enzyme itself as well.
Asunto(s)
ARN Polimerasas Dirigidas por ADN/biosíntesis , Escherichia coli/enzimología , Mutación , GenesRESUMEN
The influence of mutations in structural genes of beta- and beta'-subunits of RNA polymerase upon the synthesis of these subunits in E. coli cells have been investigated. An amber-mutation ts22 in the beta-subunit gene decreases the intracellular concentration of this subunit and the rate of its synthesis. At the same time the concentration and the rate of beta'-subunit synthesis is increased. These facts suggest the compensating activation of the synthesis of RNA polymerase subunits that takes place under the conditions of deficiency in one of the subunits. Reversions, as well as more effective suppression of ts22 amber-mutation achieved by streptomycin addition or substitution of su2 by sul result in a rise in the concentration and the rate of beta-subunit formation. This is accompanied by a drop in the concentration and the role of beta'-subunit synthesis. tsX missense motation in the beta'-subunit gene alters the properties of the enzyme increasing at the same time the concentration and the rate of synthesis of both subunits, particularly at nonpermissive temperature. This points to an inversely proportional relationship between the rate of synthesis of RNA polymerase subunits and total intracellular activity of the enzyme. Extra subunits are rapidly degraded in ts22 and tsX mutants.
Asunto(s)
ARN Polimerasas Dirigidas por ADN/biosíntesis , Escherichia coli/enzimología , Genes , Mutación , Especificidad de la EspecieRESUMEN
A comparative radioautographic study of the RNA precursors incorporation on polytene chromosomes of Drosophila in vivo in the cells of salivary glands, and in vitro during incubation of E.coli RNA polymerase on slides with fixed chromosomes was performed.--The pattern of in vivo 3H-uridine incorporation on different sections of the chromosomes drastically differed from the in vitro 3H-UTP incorporation which seems to be much more related to DNA content of the individual small sections. In both cases puffing of the loci resulted in the increase of RNA synthesis but in vitro only 2-3 fold and in vivo much more. Hence, RNA synthesis in vitro was unspecific and did not reflect the in vivo RNA synthesis.--On the other hand, E.coli RNA polymerase completely mimics in vitro the dosage compensation phenomenon making twice as much RNA on one X-chromosome of males (1X2A) as on each of X-chromosomes of diploid (2X2A) and triploid (3X3A) females and super-females (3X2A), and the intermediate amount of RNA on each of X-chromosomes of intersexes (2X3A). It is suggested that the differences in the in vitro template activity of X-chromosomes of cells with different X:A ratio are due to different extent of condensation of their deoxyribonucleoprotein (DNP). Yet, both male and each of female X-chromosomes bind the same amount of thymus histone FI labelled with fluorochrome which indicates that they contain the same amount of "open" regions with exposed chromosomal DNA accessible to external proteins.--On the basis of these observations a hypothesis is put forward which suggests that RNA transcription in animal chromosomes is regulated at two levels by different mechanisms; the first one controls the extent of condensation of DNP of genetic loci and determines their competence to the second mechanism which involves the action of gene-specific activator proteins. According to this hypothesis the phenomenon of dosage compensation of sex-linked genes is due to decondensation of DNP of male X-chromosome which renders its loci twice as responsive to activators as compared to the same loci in females.
Asunto(s)
Cromosomas/metabolismo , ARN/biosíntesis , Animales , ARN Polimerasas Dirigidas por ADN/metabolismo , Drosophila melanogaster/citología , Escherichia coli/enzimología , Femenino , Histonas/metabolismo , Técnicas In Vitro , Masculino , Cromosomas Sexuales/metabolismo , Moldes Genéticos , Transcripción GenéticaRESUMEN
The problem to be reviewed in this study concerns the mechanism of regulation of gene activity relied on the structural changes of the chromatin. The role of histones in the regulation of transcription is discussed on the basis of the results obtained by the authors and literature data. In particular, the results are presented of the investigations of decrease of the histone amount in the cell nucleus using the deficiency of histone structural genes. This leads both to the increase of the X-chromosome template activity and the inhibition of variegated position effect. The latter is also inhibited by feeding of larvae with T2-DNA. It is supposed that the chromatin structure is a mechanism of epigenetic changes and the gene inactivation due to the position effect inherited in cell lineages in an example of such epigenetic changes.
Asunto(s)
Drosophila/fisiología , Animales , Catálisis , Cromosomas/ultraestructura , ARN Polimerasas Dirigidas por ADN , Escherichia coli/enzimología , Femenino , Genes , Histonas/biosíntesis , Masculino , ARN/biosíntesis , Cromosomas Sexuales , Transcripción GenéticaAsunto(s)
Cromosomas/metabolismo , Animales , Fusión Celular , Línea Celular , Cromosomas/enzimología , Colifagos/enzimología , ADN Nucleotidiltransferasas/metabolismo , Reparación del ADN , Replicación del ADN , ARN Polimerasas Dirigidas por ADN/metabolismo , Desoxirribonucleasas/metabolismo , Escherichia coli/metabolismo , Genes Reguladores , ARN Ribosómico/metabolismo , Recombinación Genética , Supresión Genética , Transcripción GenéticaRESUMEN
Some problems of molecular genetics are considered. A special attention is paied to enzymology of genetic processes, in particular, to the mechanism of DNA replication, gene ingeneering and the structure and activity regulation mechanisms of genetic loci in higher organisms.