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N G Shostak

Publications and source records attributed to N G Shostak.

18 recordsLinked to original sources
PubMed2000

[Generation of Kruppel phenocopies by injecting into Drosophila embryos RNA complementary to mRNA in parallel orientation].

RNA preparations synthesized in vitro were used to study the influence of RNA interference on the Kruppel gene activity in Drosophila embryos. RNA complementary in parallel orientation to the mRNA fragment proved to induce the development of Kruppel phenocopies. The data obtained indicate that mechanisms of specific regulation of gene activity exist in Drosophila cells, which are sensitive to the formation of both parallel and antiparallel RNA-RNA duplexes that include mRNA of the corresponding gene.

Animals↗
PubMed1999

[Detection of a new tissue-specific enhancer in the ct6 region of the regulatory region of the drosophila cut locus].

The cut locus of Drosophila is an interesting example of a complex eukaryotic locus responsible for the development of many tissues and organs. Most of this locus is regulatory. The entire locus was cloned by Tchurikov et al. in 1986 and Blochlinger et al. in 1988. The wing ctn enhancer located 80 kb upstream of the promoter was earlier found in a 2.7 kb EcoRI-BamHI DNA fragment. The locus region 65-80 kb remote from the promoter was assumed to control the development of wings and vibrissae. We have found a new enhancer region in the ct6 region of the locus, which was in a 5 kb BamHI-EcoRI DNA fragment adjacent to the ctn enhancer. This region is responsible for the expression of the reporter lacZ gene in many tissues and organs at all stages of Drosophila development (at least in the intestine, Malpighian tubules, thoracic and abdominal sensory organs, thoracic ganglia and in ring glands). Thus, the region located 75 kb upstream of the promoter has some properties of the locus control region (LCR).

Animals↗
PubMed1995

A relatively small 5' regulatory region of esterase S gene of Drosophila virilis determines the specific expression as revealed in transgenic experiments.

Expression of the esterase S gene of Drosophila virilis was studied in transgenic experiments. Truncated genomic copy of this gene including 400 bp of 5' regulatory region was integrated into the genome of Drosophila melanogaster. The products of the transferred gene were detected. It was found that strict temporal and tissue specificity of the esterase S gene expression is conserved in transformed flies. The results suggest that this specificity is evidently determined by the regulatory region of the esterase S gene and controlled by cis mechanism.

Animals↗
PubMed1995

The expression of esterase S gene of Drosophila virilis in Drosophila melanogaster.

Drosophila melanogaster was transformed with the esterase S gene from Drosophila virilis. This gene is strongly activated in ejaculatory bulbs of mature males of Drosophila virilis. The closely related gene from Drosophila melanogaster is activated in ejaculatory ducts. The tissue- and stage-specific expression of incomplete genomic copy of the esterase S gene integrated into the Drosophila melanogaster genome is the same as in Drosophila virilis. These data show that tissue and stage specificity is determined by relatively small 5' regulatory region of the esterase S gene. The comparison between deduced amino-acid sequences of the esterase S of Drosophila virilis and esterase 6 of Drosophila melanogaster was performed. These sequences revealed 50% homology.

Amino Acid Sequence↗
PubMed1994

[Introduction of a single transpositionally-active copy of MDG4 into the genome of a stable line of Drosophila melanogaster causes genetic instability].

A previously described system of a Drosophila melanogaster mutative strain (MS), which originates from a stable strain (SS), is characterized by genetic instability caused by transposition of the retrotransposon gypsy. New unstable strains were obtained by microinjections of the gypsy transposable copy into SS embryos. In situ hybridization experiments revealed amplification and active transposition of gypsy in SS derivatives. At the same time, introduction of the gypsy transposable copy into another stable strain (208) did not lead to appearance of genetic instability. Genetic instability in the MS system is apparently induced by a combination of two factors: the presence of a gypsy transposable copy and mutation(s) in the gene(s) regulating its transpositions.

Animals↗
PubMed1994

[Preparation and primary genetic analysis of Drosophila melanogaster transformants line w'lz(b)/XXywf, containing mini-white genes, integrated in the genome during P-element-dependent transformation].

Transformation of Drosophila melanogaster using P-element-based vectors yielded 129 sublines, which carried mini-white gene copies in the different genome regions. Dependence of mini-white gene expression on the location, gene dosage, and sex of the transformed individuals was analyzed. The mutation lzb was shown to suppress mini-white gene expression, the degree of suppression depending on the location and dosage of the mini-white gene.

ATP-Binding Cassette Transporters↗
PubMed1976

[Transport RNA in early embryogenesis of fish. 3. Certain problems of regulation of RNA synthesis at the early stages of development of the loach (Misgurnus fossilis (1)].

tRNA synthesis in the early loach embryos of different ploidy and factors of the activation of synthesis and the maturation of tRNA molecules at the mid-blastula stage have been studied. tRNA synthesis is activated at the early- and mid-blastula and in the beginning of gastrulation. The normal activation of synthesis and maturation of tRNA molecules require the embryo to be maintained in the contact with the yolk at the earlier developmental stages. The methionine starvation may be one of the factors limiting the rate of tRNA maturation. The activity of tRNA synthesis during blastulation was shown to depend on gene dosage. At this stage the paternal and maternal tRNA genes are transcribed independently. In the beginning of gastrulation, the type of tRNA synthesis control markedly changes and the effect of gene dose compensation manifests itself, that is typical for the control of rRNA synthesis as well. The data obtained are discussed with respect to the state of protein synthesizing system at the moment of activation of specific protein syntheses with the onset of morphogenesis.

Animals↗
PubMedDate not supplied

[The relative content of oocyte and somatic 5S rRNA at different stages of embryonic development as an index of the replacement of maternal ribosomes by ribosomes of the embryo in the loach].

Relative content of the oocyte and somatic 5S rRNA in loach Misgurnus fossilis L. during development was determined electrophoretically. Embryos before hatching contain 70% and swimming larvae no less than 50% of the oocyte 5S rRNA. We assume that the relative content of 5S rRNA fractions reflects the proportion between ribosomes synthesized during oogenesis and those synthesized in embryos and larvae. We calculated using previous data (Timofeeva, Kafiani, 1964) the rates of maternal ribosome decay and ribosome synthesis in the embryo. During organogenesis these rates appear to be 1.17-1.09 x 10(6) and 1.7 x 10(6) molecules/sec per embryo, respectively.

Animals↗
PubMedDate not supplied

[Intragenomic polymorphism of the primary structure of 5S rRNA gene variants of the loach (Misgurnus fossilis L.). Determination of the transcriptional activity].

The primary structure of 12 cloned repeats of loach oocyte 5S rRNA genes was determined. The heterogeneity of nucleotide sequences was revealed in the coding regions and spacer of the genes. The results of the study on in vivo transcriptional activity of the cloned 5S rRNA gene variants are consistent with the localisation of site specific base substitutions in the coding part affecting the transcription. We have compared the nucleotide sequences of loach 5S rRNA gene variants and of Xenopus laevis, X. borealis and Bombyx mori 5S genes which can be actively transcribed in X. laevis oocyte nuclei. As a result we could propose a consensus nucleotide sequence in the internal control region (from 45-th up to 100-th nucleotide) of the eukaryotic 5S rRNA gene. This sequence comprises a RNA-polymerase III promotor and stretches interacting with transcriptional factors. We have considered the base substitutions in the nucleotide sequences of 5S gene variants exerted on the experimental model of loach 5S rRNA secondary structure. All base substitutions in actively transcribed genes do not influence the general double-stranded structures of the transcripts. However in 5S RNA transcripts from genes with low transcriptional activity base substitutions affecting the box c RNA-polymerase III promoter destroy hairpin II interacting with ribosomal proteins. We have concluded that two factors can restrict the divergency of 5S rRNA genes: (1) conservation of the nucleotide sequence in the gene internal control region, and (2) conservation of the general double stranded structures in 5S rRNA transcripts.

Animals↗
PubMedDate not supplied

[5S genes of the loach: determination of the primary structure of the transcription termination region and nontranscribed spacer].

The primary structure of a 5S gene spacer has been determined by sequencing three cloned 5S rDNA fragments of the loach genome. The region of the spacer adjacent to the 3'-termini of the gene structural part was shown to comprise an AT-rich sequence (24 bp long) including an oligo (T)6-9 block corresponding to the terminator of RNA polymerase III. The results supported our previous data about the 5S rRNA precursor synthesis during the transcription of cloned 5S rDNAs injected into oocyte nuclei. The comparative sequence analysis revealed a homology between the spacer region from -54 to -26 bp and the 5'-termini (1-18 bp) and the 3'-termini (108-117 bp) stretches of the gene coding region. In addition, both the coding part and nontranscribed spacer of 5S DNA include highly diversed repeats which are homologous to the 3'-termini sequence (111-+8 bp) of the gene. Apparently the nontranscribed spacer of loach 5S genes derived in evolution from numerous replicated 5S genes as a result of subsequent base elimination and substitution in the most of the 5S rRNA coding sequences.

Animals↗
PubMedDate not supplied

[Organization of genes coding for 5S rRNA in the loach Misgurnus fossilis L].

The organization of 5S rRNA genes in the loach Misgurnus fossilis L. was studied. 5S rDNA was cloned in Escherichia coli using the HindIII-fragments of loach genome DNA fused into the plasmid pBR322 restricted at the same site. The recombinant clones were tested by colony hybridization. The presence of the 5S rDNA structural sequences in cloned fragments was determined by the Southern procedure of hybridization with 5S [32P]rRNA of the loach and transcription in the oocyte test system. It was found that the size of 5S rDNA repetitive units corresponds to 240-250 bp and 450-460 bp. By the CsCl centrifugation and restriction analysis it was shown that the 5S genes in the loach genome are arranged in clusters (5-30 repeats per cluster), the smaller repeat was found to contain one coding sequence while the larger repeat contains two coding sequences of 5S rDNA.

Animals↗