Biomedical subjects

V A Gvozdev

Publications and source records attributed to V A Gvozdev.

At least 37 records · Page 2Linked to original sources

PubMed1997

The Su(Ste) repeat in the Y chromosome and betaCK2tes gene encode predicted isoforms of regulatory beta-subunit of protein kinase CK2 in Drosophila melanogaster.

We report an exon-intron structure of the Su(Ste) repeat capable of encoding an isoform of the beta-subunit of protein kinase CK2. The predicted Su(Ste) gene product contains a drastically changed amino acid sequence of the N-terminal fragment as compared to the earlier described bCK2tes gene considered to be an ancestor of the Su(Ste) repeats. The following peculiarities of molecular divergence of the Su(Ste) and betaCK2tes genes are revealed: damages of the autophosphorylation site; usage of an alternative splicing site instead of a damaged one; conservation of the zinc finger domain in spite of local ORF alterations.

Amino Acid Sequence↗

PubMed1997

Acquisition and amplification of a testis-expressed autosomal gene, SSL, by the Drosophila Y chromosome.

The acquisition of autosomal fertility genes has been proposed to be an important process in human Y chromosome evolution. For example, the Y-linked fertility factor DAZ (Deleted in Azoospermia) appears to have arisen after the transposition and tandem amplification of the autosomal DAZH gene. The Drosophila melanogaster Y chromosome contains tandemly repeated Su(Ste) units that are thought to affect male fertility as suppressors of the homologous X-linked Stellate repeats. Here we report the detection of a testis-expressed autosomal gene, SSL [Su(Ste)-like], that appears to be an ancestor of the Y-linked Su(Ste) units. SSL encodes a casein kinase 2 (CK2) beta-subunit-like protein. Its putative ORF shares extensive (45%) homology with the genuine beta-subunit of CK2 and retains the conserved C-terminal and Glu/Asp-rich domains that are essential for CK2 holoenzyme regulation. SSL maps within region 60D1-2 of D. melanogaster and D. simulans polytene chromosomes. We present evidence that SSL was derived from the genuine betaCK2 gene by reverse transcription. This event resulted in the loss of the first three introns in the coding region of the SSL ancestor gene. Evolutionary analysis indicates that SSL has evolved under selective pressure at the translational level. Its sequence, especially in the 3' region, is much closer to the Y-linked Su(Ste) tandem repeats than to the betaCK2 gene. These results suggest that the acquisition of testis-specific autosomal genes may be important for the evolution of Drosophila as well as human Y chromosomes.

Amino Acid Sequence↗

PubMed1997

Segmented gene conversion as a mechanism of correction of 18S rRNA pseudogene located outside of rDNA cluster in D. melanogaster.

The peculiarities of the sequences of 18S rDNA included in a 90-kb DNA segment cloned in YAC vector are described. This heterochromatic segment is situated on the X chromosome distal to the main rDNA cluster. The pseudo 18S rDNA sequence comprised undamaged stretches of rDNA interspersed with segments characterized by high density of nucleotide substitutions and insertions/deletions. The observed patchwork arrangement of unaltered rDNA sequences was considered as evidence of segmented gene conversion events between the normal and damaged genes which are thought to constitute one of the mechanisms of rDNA array homogenization. The 18S rDNA fragment (510 bp) located nearby, homologous to the internal, undamaged part of pseudo 18S rDNA, carries comparable density of randomly distributed nucleotide substitutions with no evidence of correction.

Animals↗

PubMed1997

Position-effect variegation in Drosophila melanogaster X chromosome inversion with a breakpoint in a satellite block and its suppression in a secondary rearrangement.

In(1LR)pn2a is a pericentric inversion with a euchromatic breakpoint in the 2E polytene region and a heterochromatic breakpoint in the right arm of the X chromosome. It is associated with position-effect variegation (PEV) of the pn, wapl, Pgd and other vital loci of the 2E region, which are relocated near the bulk of the X heterochromatin. Cytological analysis showed that the rearrangement brings the 1A-2E euchromatic segment directly into contact with a major portion of the h34 block, a heterochromatic region that is positively stained by the N-banding technique and contains the AAGAG satellite sequences. Molecular cloning revealed the presence of a new junction between euchromatin and AAGAG satellite sequences and demonstrated that the euchromatic breakpoint of In(1LR)pn2a lies in the vinculin gene. In the X ray-induced secondary rearrangement In(1LR)r30, consisting of a pericentric inversion superimposed on In(1LR)pn2a, the h34 material remains associated with the 2E region but is separated from the rest of the X heterochromatin. In this case, the pn, wapl and Pgd loci no longer variegate, suggesting that the satellite-containing h34 region is not able per se to induce detectable PEV on the adjacent euchromatic genes.

Animals↗

PubMed1997

Insect mucin-type glycoprotein: immunodetection of the O-glycosylated epitope in Drosophila melanogaster cells and tissues.

A mucin-type glycoprotein (GP) from cultured embryonic cells of Drosophila melanogaster was isolated and used to raise monoclonal antibodies (MAbs). Epitope(s) recognized by MAbs were sensitive to the treatment by O-glycanase, which specifically cleaves off O-linked mucin-type Gal(beta 1,3)GalNAc disaccharide, representing the major part of the carbohydrate moiety of Drosophila GP. Using high-affinity MAbs against carbohydrate epitopes of the Drosophila mucin GP we demonstrated its accumulation in culture medium, as well as in cultured cells, which proved to be regulated by 20-hydroxyecdysone. Mucin GPs carrying Gal(beta 1,3)GalNAc disaccharide recognized by the MAbs were immunochemically localized in several Drosophila tissues of ectodermal, mesodermal and germ line origin, including epidermal and follicle cells capable of their secretion.

Animals↗

PubMed1997

Heterochromatic Stellate gene cluster in Drosophila melanogaster: structure and molecular evolution.

The 30-kb cluster comprising close to 20 copies of tandemly repeated Stellate genes was localized in the distal heterochromatin of the X chromosome. Of 10 sequenced genes, nine contain undamaged open reading frames with extensive similarity to protein kinase CK2 beta-subunit; one gene is interrupted by an insertion. The heterochromatic array of Stellate repeats is divided into three regions by a 4.5-kb DNA segment of unknown origin and a retrotransposon insertion: the A region (approximately 14 Stellate genes), the adjacent B region (approximately three Stellate genes), and the C region (about four Stellate genes). The sequencing of Stellate copies located along the discontinuous cluster revealed a complex pattern of diversification. The lowest level of divergence was detected in nearby Stellate repeats. The marginal copies of the A region, truncated or interrupted by an insertion, escaped homogenization and demonstrated high levels of divergence. Comparison of copies in the B and C regions, which are separated by a retrotransposon insertion, revealed a high level of diversification. These observations suggest that homogenization takes place in the Stellate cluster, but that inserted sequences may impede this process.

Amino Acid Sequence↗

PubMed1997

The beta CK2tes gene encodes the tissue-specific regulatory subunit of casein kinase 2 in Drosophila melanogaster.

The beta CK2tes gene encodes a new variant of the tissue-specific regulatory beta-subunit of casein kinase 2 (CK2). The beta CK2tes open reading frame comprises nucleotide stretches encoding for the conservative polypeptide motifs characteristic for the CK2 beta-subunit including the Glu/Asp rich region responsible for regulation of CK2, C-terminal fragment responsible for binding to the catalytic alpha-subunit, and "zinc finger" motif. Unlike conserved sequences of CK2 beta-subunits in other organisms the beta CK2tes polypeptide has no autophosphorylation site or other putative phosphorylation sites. beta CK2tes is expressed only in testes, whereas beta CK2 expression is maximal at embryonic stages and is detected also in larvae. We suggest that beta CK2tes determines substrate specificity of CK2 and/or CK2 activity during spermatogenesis in Drosophila.

Amino Acid Sequence↗

PubMed1996

Mucin-type glycoprotein from Drosophila melanogaster embryonic cells: characterization of carbohydrate component.

A secreted glycoprotein (GP) with apparent molecular mass of 90 kDa produced by cultured embryonic cells of Drosophila melanogaster was isolated and partially characterized. GP is enriched by Ser + Thr and Pro residues that constitute up to 30% of the total number of amino acids. An abundant carbohydrate moiety (40% of molecular mass) is mainly represented by vertebrate mucin-type O-linked disaccharide units Gal(beta 1-3)-GalNAc, occupying about a half of the total number of Ser+Thr residues and rendering the GP molecule high resistance to protease action. A few of N-glycans are also present in GP. These characteristics allow to consider the Drosophila GP (termed 'mucin-D') as a first representative of invertebrate mucin-type glycoproteins.

Amidohydrolases↗

PubMed1995

Structure of the Drosophila melanogaster annexin X gene.

The annexin X gene was cloned in the P1 recombinant phage carrying a genomic sequence of approximately 70 kb long. This DNA fragment encompasses at least two annexin X copies and several 7.8-kb tandem units represented by an anonymous sequence fused to the 3' truncated part of the annexin X gene. The proteins of annexin family contain a variable amino-terminal domain and a core domain; the latter includes four structurally conserved repeats that presumably arose as a result of duplications. The annexin X gene of Drosophila is about 2 kb long and contains four exons. Exon 1 encodes four amino-terminal amino acids, exon 2 encodes the remaining part of the amino-terminal domain and the three conserved repeats, and exon 3 and exon 4 encode the fourth repeat. The positions of introns 2 and 3 are strictly conserved with respect to both the amino acid position and codon phase as compared to introns 10 and 12 of the fourth repeat in vertebrate annexin genes. We propose the existence of a primordial annexin coding structure comprising at least two introns whose duplications during evolution have been followed by the loss of ancient introns in the first three repeats of Drosophila and vertebrates. Acquisition of new introns in vertebrates is supposed taking into account that exon borders are not found at homologous locations in four repeats of a given vertebrate annexin. Transcription of the annexin gene was detected in embryonic cell cultures. No profound effects of ecdysterone on the annexin X message content in cell cultures were observed.

Amino Acid Sequence↗

PubMed1995

[Glycoproteins from Drosophila melanogaster cell culture contains O-bound carbohydrate chains of the Gal(beta1-3)GalNAc type].

The glycoprotein from cultured cells of D. melanogaster, also detected in various insect tissues as a component of the extracellular matrix, was characterized as a mucin-type glycoprotein not yet described in invertebrates. This glycoprotein with an apparent molecular mass of approximately 90 kDa contains about 40% of carbohydrates, largely represented mainly by GalNAc and Gal; its polypeptide moiety is enriched with Thr, Ser, Pro and Gly. An analysis of oligosaccharides liberated by treatment of the glycoprotein with alkaline NaBH4 or O-glycanase (endo-alpha-N-acetylgalactosaminidase) revealed Gal(beta 1-3)GalNAc as the major type of the sugar chains. About half of the Thr + Ser residues in the glycoprotein were estimated as O-glycosidically linked with the disaccharide units.

Animals↗

PubMed1994

Structure, molecular evolution and maintenance of copy number of extended repeated structures in the X-heterochromatin of Drosophila melanogaster.

The 60 kb repeats located in the distal heterochromatin of the X chromosome of Drosophila melanogaster were cloned in overlapping cosmids. These regions, designated as SCLRs, comprised the following types of repeated elements: Stellate genes, which are known to be involved in spermatogenesis; copia-like retrotransposons; LINE elements, including amplified Type I rDNA insertions; and rDNA fragments. The following steps in SCLR formation were hypothesized: insertion of mobile elements into the rDNA and Stellate gene clusters; internal tandem duplication events; recombination between the rDNA cluster and Stellate tandem repeat; and amplification of the whole SCLR structure. There are about nine SCLR copies per haploid genome, but there is approximately a twofold variation in copy number between fly stocks. The SCLR copy number differences between closely related stocks are suggested to be the result of unequal sister chromatid exchange (USCE). The restricted variation in SCLR copy number between unrelated stocks and the absence of chromosomes free of SCLRs suggests that natural selection is active in copy number maintenance.

Animals↗

PubMed1994

["Adaptive transposition" of retrotransposons in the Drosophila melanogaster genome accompanying the increase in features of adaptability].

Two cases of spontaneous transpositions of MDG1, MDG3, and copia retrotransposons were detected in Drosophila melanogaster lines derived from the nonadaptive NA line and marked by recessive visible mutations. The transpositions were accompanied by a dramatic increase in individual fitness (competitive success). In independent instances of MDG1 transpositions, the location patterns of new sites were similar. These results confirm the existence of adaptive transpositions that were demonstrated earlier for the NA line that carried no visible markers.

Adaptation, Physiological↗

PubMed1994

[Variability of rDNA genes, detected as a result of analyzing a pseudogene nucleotide sequence in Drosophila melanogaster].

A pseudogene bearing the bulk of the 18S RNA gene was detected outside the rDNA cluster. It comprised irregularly distributed nucleotide substitutions as well as short insertions and deletions. No sequence alterations were observed in the 5' region of the pseudogene, whereas the frequency of substitutions and alterations per nucleotide number in the 3' region and in the middle of the sequence was 7.6% and 1.8%, respectively. The observed sharp irregularity in distribution of substitutions and alterations was considered the result of successive recombinations between the functional 18S rRNA gene and its diverged or damaged variants. This phenomenon provides experimental evidence that recombinations between the pseudogene and functioning repeats of rDNA are implicated in the mechanism of rDNA sequence correction. A segment of the pseudogene sequence was shown to contain substitutions primarily in regions coding for single-strand parts of the RNA molecule. The same segment contained a deletion and an insertion of a nucleotide, approximating it to the most of the studied eukaryotic 18S rRNA sequences. These observations allowed us to supposed that a structural rDNA variant, a fragment of which appears in the pseudogene sequence, is present in the genome. The data obtained suggest both the presence of 18S rDNA variants, and recombination between them, determining the concerted evolution of rRNA genes.

Animals↗

PubMed1992

Structural organization and diversification of Y-linked sequences comprising Su(Ste) genes in Drosophila melanogaster.

Expression of the X-linked repeated Stellate (Ste) genes, which code for a protein with 38% similarity to the beta-subunit of casein kinase II, is suppressed by the Su(Ste) locus on the Y chromosome. The structure and evolution of the Y-linked repeats in the region of the Su(Ste) locus were studied. The 2800 bp repeats consist of three main elements: the region of homology to the Ste genes, an adjacent AT-rich, Y-specific segment, and mobile element 1360 inserted in the Ste sequence. Amplification of repeats was followed by point mutations, deletions, and insertions of mobile elements. DNA sequencing shows that these repeats may be considered as Ste pseudogenes or as damaged variants of a putative gene(s) encoding a protein quite different from the Ste protein as a result of an alternative splicing pattern. A comparison of 5 variants of the Y-Su(Ste) repeats shows a number of recombination events between amplified and diverged sequences that could be due to either multiple unequal mitotic sister-chromatid exchanges or to gene conversion. It is a first demonstration on a molecular level of these processes occurring in heterochromatic non-rDNA tandemly organized sequences in an eukaryotic genome.

Animals↗

PubMed1992

[Comparative analysis of the localization and mobility of retrotransposons in sibling species Drosophila simulans and Drosophila melanogaster].

The distribution of four retrotransposon families (MDG1, MDG3, MDG4 and copia) on polytene chromosomes of different (from 9 to 15) Drosophila simulans strains is studied. The mean number of MDG1 and copia euchromatic hybridization sites (3 sites for each element) is drastically decreased in D. simulans in comparison with D. melanogaster (24 and 18 sites respectively). The mean number of MDG3 sites of hybridization is 5 in D. simulans against 12 in D. melanogaster. As for MDG4 both species have on the average about 2-3 euchromatic sites. The majority of MDG1 and copia and about a half of MDG3 euchromatic copies are localized in restricted number of sites (hot spots) on D. simulans polytene chromosomes. In D. melanogaster these elements are scattered along the chromosomes though there are some hot spots too. It appears that euchromatic copies of MDG1 and copia are considerably less mobile in D. simulans in contrast to D. melanogaster. Some common hot spots of retrotransposon localization in D. simulans and D. melanogaster were earlier described as intercalary heterochromatin regions in D. melanogaster. The level of interstrain variability of MDG4 hybridization sites is comparable in both species. Comparative blot-analysis of adult and larval salivary gland DNA shows that MDG1 and copia are situated mainly in euchromatic regions of D. melanogaster chromosomes. In D. simulans genome they are located mainly in heterochromatic regions underreplicated in salivary gland polytene chromosomes. There are interspecies differences in the distribution of retrotransposons in beta-heterochromatic chromosome regions.

Animals↗

PubMed1991

The sources of genetic variability in highly inbred long-term selected strains of Drosophila melanogaster.

A highly inbred, long-term selected for low fitness strain LA of Drosophila melanogaster possesses a significant mutational load and unusually high rates of spontaneous mutability as revealed by CyL/Pm method. Our results indicate that during cross of CyL/Pm to LA strains, destabilization of copia-like and mobile elements and induction of H-E hybrid dysgenesis take place. The role of these processes in causing considerable genetic variability of LA strain is discussed.

Animals↗

PubMed1991

[Maintenance of the copy number of retrotransposon MDG3 in the Drosophila melanogaster genome].

The genomes of laboratory stocks and natural population of Drosophila melanogaster contain 8-12 copies of retrotransposon MDG3 detected by in situ hybridization. Construction of genotypes with decreased MDG3 copy number using X-chromosome and chromosome 3 free of MDG3 copies results in appearance of hybrid genomes carrying up to 7-10 copies, instead of 2-4 copies expected. New MDG3 copies are detected in different genome regions, including the 42B hot spot of their location. The chromosomes, where new clusters of MDG3 were observed, carry conserved "parental pattern" of MDG1 arrangement. The data obtained suggest the existence of genomic mechanism for maintenance of retrotransposon copy number on a definite level.

Animals↗

PubMed1989

Heterochromatic regions in different Drosophila melanogaster stocks contain similar arrangements of moderate repeats with inserted copia-like elements (MDG1).

Seven out of twenty 30-50 kb genome fragments with an MDG1 copia-like element cloned in cosmids were found to carry homologous sequences which belong to a new family of non-mobile heterochromatic moderate repeats (the HMR family). These repeats along with the MDG1 copies inserted in them are under-replicated in polytene chromosomes. Such repeats may also be located in the intercalary heterochromatin site 12E of the X chromosome. Chromosomal heterochromatic regions are enriched with one of the two main genomic variants of MDG1, MDG1het, identifiable by EcoRI restriction. From Southern DNA blot analysis the number of MDG1het copies and their sites within the heterochromatin are invariant in all the stocks examined, while there is not a single MDG1 site along the polytene chromosomes shared by all the stocks in question.

Animals↗