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E S Beliaeva

Publications and source records attributed to E S Beliaeva.

At least 19 recordsLinked to original sources
PubMed2006

[Contribution of the SuUR gene to the organization of epigenetically repressed regions of Drosophila melanogaster chromosomes].

A significant portion of a eukaryotic genome is silent (epigenetically repressed). In Drosophila melanogaster, this portion includes mainly regions of pericentric and intercalary heterochromatin and euchromatin regions subject to position-effect variegation. Detailed study of the organization of intercalary heterochromatin regions of Drosophila melanogaster polytene chromosomes started from the discovery of the SuUR gene (Suppressor of UnderReplication). The ability of the SuUR mutation to suppress underreplication in intercalary heterochromatin regions was used for molecular tagging of these regions. We showed that underreplicated intercalary heterochromatin regions contained silent unique genes and retained the features of late replication and transcriptionally inactive chromatin state in various cell types. Over 50% of these regions contain unique genes clustered on the base of coordinated expression. The origin of clusters and putative mechanisms of their gene expression are discussed. Data on the SuUR gene, its expression, and effect on polytene chromosome structure and replication are summarized.

Animals↗
PubMed2003

[Heterochromatin, gene position effect and gene silencing].

Genomes of higher eukaryotes consist of two types of chromatin: euchromatin and heterochromatin. Heterochromatin is densely packed material typically localized in telomeric and pericentric chromosome regions. Euchromatin transferred by chromosome rearrangements in the vicinity of heterochromatin is inactivated and acquires morphological properties of heterochromatin in the case of position effect variegation. One of the X chromosomes in mammal females and all paternal chromosome set in coccides become heterochromatic. The heterochromatic elements of the genome exhibit similar structural properties: genetic inactivation, compaction, late DNA replication at the S stage, and underrepresentation in somatic cells. The genetic inactivation and heterochromatin assembly are underlain by a specific genetic mechanism, silencing, which includes DNA methylation and posttranslational histone modification provided by the complex of nonhistone proteins. The state of silencing is inherited in cell generations. The same molecular mechanisms of silencing shared by all types of heterochromatic regions, be it unique or highly repetitive sequences, suggest the similar organization of these regions. No type of heterochromatin is a permanent structure as they all are formed at the strictly definite stages of early embryogenesis. Based on the bulk of evidence accumulated today, heterochromatin can be regarded as a morphological manifestation of genetic silencing.

Animals↗
PubMed2001

[Modeling dark puffs using P-transposons in Drosophila melanogaster polytene chromosomes].

Modeling of morphologically unusual "dark" puffs was conducted using Drosophila melanogaster strains transformed by construct P[ry; Prat:bw], in which gene brown is controlled by the promoter of the housekeeping gene Prat. In polytene chromosomes, insertions of this type were shown to form structures that are morphologically similar to small puffs. By contrast, the Broad-Complex (Br-C) locus, which normally produce a dark puff in the 2B region of the X chromosome, forms a typical light-colored puffs when transferred to the 99B region of chromosome 3R using P[hs-BRC-z1]. A comparison of transposon-induced puffs with those appearing during normal development indicates that these puff types are formed via two different mechanisms. One mechanism involves decompaction of weakly transcribed bands and is characteristic of small puffs. The other mechanism is associated with contacts between bands adjacent to the puffing zone, which leads to mixing of inactive condensed and actively transcribed decondensed material and forming of large dark puffs.

Animals↗
PubMed2001

[Interline differences in morphology of the precentromeric region of polytene X-chromosome in Drosophila melanogaster salivary glands].

Morphology of the Drosophila melanogaster polytene X chromosome section 20 in normal flies, in strains carrying inversions that break pericentric heterochromatin at different points, and at the background of the Su(UR)ES mutation has been examined. In all of the strains carrying the Su(UR)ES mutation section 20 displayed a distinct banding pattern till to the section 20F, while in the wild-type strains this region was represented by beta-heterochromatin. The strains carrying different inversions substantially differed in the number and morphology of bands forming section 20. In the Su(UR)ES mutants the most proximal X chromosome euchromatin gene, su(f), is mapped to the boundary between sections 20E and F, while rDNA forming the middle part of the X chromosome mitotic heterochromatin is located in the proximal part of section 20F. All large bands observed in section 20 of the w; Su(UR)ES strain were also present in In(1)sc4; Su(UR)ES, which breaks heterochromatin in the distal part. Hence, the bands of polytene chromosome section 20 are virtually devoid of mitotic heterochromatin.

Animals↗
PubMed2000

[Position effect variegation of the mosaic type, arising as a result of transposition AR4-24P[white, rosy] in the Drosophila melanogaster genome].

A line with the mosaic expression of the white+ transgene was obtained by inducing transposition of the AR4-24P[white, rosy] transposon and was used for the second round of induction. As a result, 57 lines with the mosaic eye pigmentation were obtained. In situ hybridization and Southern blotting showed that genomic DNA fragments flanking AR4-24 were, in some cases, transposed together with the transposon. A spontaneous loss of these fragments resulted in reversion to the wild-type phenotype. The mosaic eye pigmentation in a line that carried the AR4-24 transposon flanked with the same fragments in region 24D1-2 was not affected by the Su(var)3-6 gene modifying position effect variegation (PEV). Other PEV modifiers, Su(var)3-9 and Su(var)2-5, had only a slight effect on PEV; Su(var)3-7 restored the wild-type phenotype. The genomic fragments captured by the transposon may contain DNA sequences that autonomously induce mosaic PEV of the white gene.

Animals↗
PubMed2000

[Effect of four doses of the Su(UR)ES gene on intercalary heterochromatin in Drosophila melanogaster].

Polytene chromosomes of salivary glands of various Drosophila melanogaster strains containing two doses of the normal Su(UR)ES allele have a constant set of intercalary heterochromatin (IHC) sites. Their DNA is underreplicated, which leads to breaks and ectopic contacts emerging at a certain rate. Almost no underreplication, breaks, or ectopic conjugation are present in mutants lacking the normal Su(UR)ES gene product. It could be expected that an increase in the number of the Su(UR)ES+ gene doses would, in turn, drastically increase ectopic conjugation and breakage. To test this hypothesis, a strain of D. melanogaster was obtained with two additional doses of Su(UR)ES+ introduced into its genome. The flies with four gene doses exhibited a considerable increase in ectopic conjugation: both the proportion of regions participating in conjugation and the number of chromosomes with numerous contact nodes were increased. As a result, chromosomes that were straight and well-stretched in homozygotes for the mutation in Su(UR)ES became twisted and wound and contained many loops or nodes. Many chromosomes were wound too tightly for cytological analysis. Four doses of Su(UR)ES+ considerably increased the number of weak "points." For example, the 2R chromosome has only 3 weak points in strains with two doses of Su(UR)ES+ and as many as 22 weak points in the strain with four doses. In the transgenic strain, the frequency of breaks in previously known weak points increased, and new breaks appeared in 19 additional sites. All new break points appeared in the regions that were earlier described as regions of late replication in the S phase.

Animals↗
PubMed1999

[Microcloning and characteristics of DNA from regions of the centromeric heterochromatin of Drosophila melanogaster polytene chromosomes].

A method of microcloning, which involves microsurgical excision of chromosome fragments, DNA amplification by means of a polymerase chain reaction (PCR), and ligation of amplified products with plasmids, was employed in studying Drosophila polytene chromosomes for the first time. Clones of the DNA library thus obtained contained inserts varying in size from 0.1 to 0.5 kb. DNA sequencing of five clones of the library showed that pericentromeric heterochromatin contained the 17.6 and 297 retrotransposons, the ninja retrotransposon characteristic of D. simulans, and two Drosophila repetitive elements, a8 and a12, the function of which remains unknown.

Amino Acid Sequence↗
PubMed1999

[Comparison of the molecular and genetic map of the 2B6-2B7-8 of Drosophila melanogaster X-chromosome].

Molecular and genetic data were compared for the 2B6-2B7-8 region of the Drosophila melanogaster X chromosome. This region contains the dor (deep orange) and swi (single wing) genes influencing ecdysterone-dependent gene expression. Genes which had not been identified previously by genetic methods were shown to be present in this region. Two novel loci, designated a6 and b6, were characterized in detail. Both genes are expressed throughout Drosophila embryogenesis. The product of b6 has a homology with mammalian pentraxins. This is the first Drosophila gene found to contain the pentraxin motif.

Amino Acid Sequence↗
PubMed1998

[Somatic pairing of homologs of the fourth chromosome as a reason for suppression of the Dubinin effect in Drosophila melanogaster].

The position effect of the cubitus interruptus (ci) gene occurs when this gene, which is normally located in the vicinity of the pericentric heterochromatin of chromosome 4, is transferred by chromosome rearrangements to euchromatin regions. Cytological aspects of this phenomenon were investigated. For six reciprocal translocations causing the position effect (Dubinin effect) of ci, the frequencies of the ectopic contacts of the translocated chromosome 4 homologue with pericentric heterochromatin were compared to the conjugation frequencies of this chromosome's homologues. The frequencies were significantly higher when the gene was transferred to proximal chromosome regions. This suggested that the suppression of the Dubinin effect in the case of translocations with euchromatin breaks in proximal chromosome regions is caused by the higher conjugation frequency of translocated and normal chromosome 4 homologues in proximal than in distal regions. The effect of genes modulo and Su(var)2-05, which are known as modifiers of the position effect variegation, on the conjugation frequency of chromosome 4 homologues was studied for three translocations. It was shown that modulo did not affect this frequency, whereas Su(var)205 significantly decreased it. Cytogenetic data confirmed the association of the ci position effect with damage in the somatic pairing of chromosome 4 homologues. These data indicate that pericentric heterochromatin participates in determination of the localization of chromosome regions in the interphase nucleus.

Animals↗
PubMed1998

[A genetic factor, suppressing DNA underreplication in Drosophila melanogaster polytene chromosomes].

The Drosophila melanogaster line carrying the In(I)scv2 was found to exhibit unique cytological phenotype distinguished by the lack of "weak" points in the intercalary heterochromatin of the salivary gland polytene chromosomes, the absence of ectopic contacts between the chromosome regions, and the occurrence of additional intercalary heterochromatin in the centromeric regions. Southern blot hybridization revealed the absence of DNA underreplication in the intercalary heterochromatin region 39E carrying the histone gene cluster. This phenotype may have arisen under the influence of a genetic factor, Su(UR), which suppressed DNA underreplication in polytene chromosomes. Genetic analysis of the inheritance of the "suppression of DNA underreplication" phenotype showed that this factor was located in the third chromosome and was expressed in a semidominant manner. Discovery of Su(UR) suggested existence of common mechanisms regulating DNA underreplication in the centromeric and intercalary heterochromatin regions containing genes that were completely inactivated during ontogeny. These results confirm the assumption of common mechanisms of epigenetic repression of highly repetitive, somewhat repetitive, and unique sequences of the Drosophila genome.

Animals↗
PubMed1996

[Effect of genetic background on mutation frequency of insertional alleles of the lozenge in Drosophila melanogaster].

We studied the effect of genetic background on mutation frequency of an unstable lz75V allele of the lozenge gene (lz; 1-27.7) isolated from natural populations of Drosophila melanogaster and its mutant derivatives lzB abd lzsl. Genetic composition of the X chromosome containing unstable alleles (X75V chromosome) was shown to affect their mutability. The region of the chromosome proximal to lozenge contains factors required for high mutability of lz75V and lzB. Substitution of a distal part of the X chromosome from a laboratory strain for a homologous part of the X75V chromosome also resulted in stabilizing lz75V, but caused an increase in mutation frequency of lzB. Association between instability of lz75V and the presence of P element with the locus was revealed by in situ hybridization. Studying effects of regulatory elements from a pi 2 P strain showed that the P cytotype is associated with a twofold to threefold decrease in mutation frequency of lzB and lzsl, but P-M hybrid dysgenesis is associated with its slight increase. Regulation of instability of the lozenge gene within the X75V chromosome was assumed to involve three levels: (1) character and topography of a mobile element inserted into the locus, (2) regulatory factors of other X-chromosomal regions, and (3) cytoplasmic factors. The results obtained are discussed in terms of regulation of transposition of mobile genetic elements.

Alleles↗
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

[Cytogenetic analysis of insertions into drosophila interband polytene chromosomes].

Using the method of P-element-mediated enhancer detection, 29 Drosophila melanogaster lines were obtained that carried P-1ArB vector insertions in chromosomes 2 and 3. The expression of the reporter gene lacZ at different developmental stages of the transformed lines was determined in color reactions for beta-galactosidase. Regions of vector integration were located using in situ hybridization. Subsequent electron-microscopic mapping of the transformed regions was performed using four lines (nos. 12, 41, 2, and 3). In the lines 12 and 41, lacZ was expressed in most tissues of embryos, larvae, and imagoes (including salivary glands), whereas in lines 2 and 3 its expression was observed only in embryos. Lines 12 and 2 showed the presence of insertions in the 85D9/10 and 86B4/6 interband regions, respectively. The absence of a novel band in line 3 could be associated with transposon integration into the band. In line 41, puffing of the transformed region was observed, which did not allow us to determine the presence of any novel structures in it. The novel structures in lines 12 and 2 looked like single bands with a similar DNA packing ratio of about 30. These bands were obviously polygenic, because the inserted vector contained four functionally different genes.

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

[Transpositions of mobile elements mdg4 (gypsy) and hobo in somatic and germ cells of a genetically unstable mutator strain of Drosophila melanogaster].

Analysis of distribution of the several families of mobile genetic elements has been performed. The analysis dealt with the X chromosomes of male progeny from the crosses of individual males of Mutator strain (MS) with attached-X females. The experimental results demonstrated different localization of the elements gypsy and hobo in the salivary gland squashes of different males-brothers. Location of other elements under study--mdg1, 412, mdg3, copia, 297, 17.6, Beagle, BS, Doc, FB, Springer--was invariant in all larvae. The analysis is equal to the study of transposition events at the level of gametes. Thus, doubtless, the capability of gypsy and hobo to transpose in germ cells of the MS individuals has been detected. Mobilization of the elements occurs at premiotic stages of gametes' development, as indicated by appearance of the clusters of transpositions. In the process of studies on coincidence of gypsy and hobo transposition acts, independent character of the elements' movement has been revealed. It has been detected in the same experiment that the distribution of the gypsy copies in different cells of the same salivary gland varies strongly. All hybridization sites were divided into two groups: "constant" sites common for all cells and "additional" ones, whose locations did not coincide in neighbouring cells of salivary gland. The existence of additional sites is major evidence of gypsy transpositions in somatic cells of MS. Transposition events have been as well discovered for hobo in somatic cells.

Animals↗