Elena S. Belyaeva

Bio: Elena S. Belyaeva is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Polytene chromosome & Heterochromatin. The author has an hindex of 33, co-authored 98 publications receiving 3271 citations.

EcR isoforms in Drosophila: testing tissue-specific requirements by targeted blockade and rescue.

Abstract: The three Drosophila EcR isoforms differ only at their N termini; thus, they share the conserved ligand-binding domain transcriptional activation function (AF2) and only differ in the unconserved A/B region, which contains a second, isoform-specific, activation function (AF1). We have developed a dominant-negative mutant EcR (EcR-DN), expressed it in flies with the GAL4/UAS system, and used it to block ecdysone signaling in eight tissues or groups of tissues. Localized EcR-DN arrests ecdysone-dependent development in the target cells and often — because of a molting checkpoint — arrests development globally. Simultaneously expressing individual wild-type EcR isoforms in the same target tissues suppresses the EcR-DN phenotype and identifies the rescuing isoform as sufficient to support the development of the target. Every isoform, and even an N-terminal truncated EcR that lacks any AF1, supports development in the fat body, eye discs, salivary glands, EH-secreting neurosecretory cells and in the dpp expression domain, implying that AF1 is dispensable in these tissues. By contrast, only EcR-A is able to support development in the margins of the wing discs, and only EcR-B2 can do so in the larval epidermis and the border cells of the developing egg chamber. In light of our results, the simplest explanations for the widespread spatial and temporal variations in EcR isoform titers appear untenable.

Intercalary heterochromatin in Drosophila: I. Localization and general characteristics

Abstract: Sites of intercalary heterochromatin (IH) in the complete set of Drosophila melanogaster polytene chromosomes were localized and studied according to the following criteria: tendency to break (weak points), ectopic pairing and late replication, the existence of repeats (in X and 2R) including those enriched with A-T bases. Correlation between these features investigated, the highest correlation coefficients found between weak point behavior, late replication, and ectopic pairing. The frequency of breaks in weak points in some IH bands was shown to be different in different tissues, strains and closely related Drosophila species. Sexual differences in morphology and manifestation of IH features were found in bands of the X chromosome: weak point behavior and participation in ectopic pairing of IH bands are an order of magnitude less frequent in male X chromosomes than in female X chromosomes. In autosomes such differences have not been observed. IH bands in male X chromosomes look more massive than the homologous ones in female X chromosomes: the DNA content of the 11A6-9 region is four times less in females than in males. The hypothesis is proposed that the specific features of intercalary heterochromatin bands are determined by tandem repetitiveness and late replication. The latter, if it occurs in a cluster of repetitions, could cause incomplete polytenization of the region and, as a consequence, breaks (or weak points) and the appearance of “adhesive ends” which may take part either in realization of ectopic contacts or in fixation of those occurring previously. Breaks caused by chromosome aberrations in regions with repeats may not result in a sharp decline of viability, so that break points of chromosome rearrangements in intercalary heterochromatin may be more frequent than in other regions.

Cytogenetic analysis of the 2B3-4-2B11 Region of the X-chromosome of Drosophila melanogaster - I. Cytology of the region and mutant complementation groups

Abstract: Larvae homozygous or hemizygous for the l(l) t435 mutation located within the early ecdysteroid puff 2B5, or carrying a deletion of the 2B5 band, die at the end of the third larval instar. In the salivary gland chromosomes of these larvae only intermoult puffs are detected. If these salivary glands are incubated in vitro with 20-OH ecdysone for 6 h the intermoult puff 68 C remains large, some early puffs (74EF and 75B) are induced to 30–40% of their normal size, other early (63F) and all late puffs (62E, 78D, 82F and 63E) are not induced at all. Puff 2B5 reaches its normal size but does not regress after 6h incubation with 20-OH ecdysone, as it does in normal stocks. The data obtained in this study show the existence of a locus (or loci) in the band (puff) 2B5 which is necessary for the normal response of the salivary gland chromosomes to the hormone 20-OH ecdysone.

Su(UR)ES: a gene suppressing DNA underreplication in intercalary and pericentric heterochromatin of Drosophila melanogaster polytene chromosomes.

Abstract: A genetic locus suppressing DNA underreplication in intercalary heterochromatin (IH) and pericentric heterochromatin (PH) of the polytene chromosomes of Drosophila melanogaster salivary glands, has been described. Found in the In(1)scV2 strain, the mutation, designated as Su(UR)ES, was located on chromosome 3L at position 34. 8 and cytologically mapped to region 68A3-B4. A cytological phenotype was observed in the salivary gland chromosomes of larvae homozygous and hemizygous for Su(UR)ES: (i) in the IH regions, that normally are incompletely polytenized and so they often break to form "weak points," underreplication is suppressed, breaks and ectopic contacts disappear; (ii) the degree of polytenization in PH grows higher. That is why the regions in chromosome arm basements, normally beta-heterochromatic, acquire a distinct banding pattern, i. e., become euchromatic by morphological criteria; (iii) an additional bulk of polytenized material arises between the arms of chromosome 3 to form a fragment with a typical banding pattern. Chromosome 2 PH reveals additional alpha-heterochromatin. Su(UR)ES does not affect the viability, fertility, or morphological characters of the imago, and has semidominant expression in the heterozygote and distinct maternal effect. The results obtained provide evidence that the processes leading to DNA underreplication in IH and PH are affected by the same genetic mechanism.

Polytene chromosomes: 70 years of genetic research.

Abstract: Polytene chromosomes were described in 1881 and since 1934 they have served as an outstanding model for a variety of genetic experiments. Using the polytene chromosomes, numerous biological phenomena were discovered. First the polytene chromosomes served as a model of the interphase chromosomes in general. In polytene chromosomes, condensed (bands), decondensed (interbands), genetically active (puffs), and silent (pericentric and intercalary heterochromatin as well as regions subject to position effect variegation) regions were found and their features were described in detail. Analysis of the general organization of replication and transcription at the cytological level has become possible using polytene chromosomes. In studies of sequential puff formation it was found for the first time that the steroid hormone (ecdysone) exerts its action through gene activation, and that the process of gene activation upon ecdysone proceeds as a cascade. Namely on the polytene chromosomes a new phenomenon of cellular stress response (heat shock) was discovered. Subsequently chromatin boundaries (insulators) were discovered to flank the heat shock puffs. Major progress in solving the problems of dosage compensation and position effect variegation phenomena was mainly related to studies on polytene chromosomes. This review summarizes the current status of studies of polytene chromosomes and of various phenomena described using this successful model.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The advantages and disadvantages of being polyploid

Abstract: Polyploids — organisms that have multiple sets of chromosomes — are common in certain plant and animal taxa, and can be surprisingly stable. The evidence that has emerged from genome analyses also indicates that many other eukaryotic genomes have a polyploid ancestry, suggesting that both humans and most other eukaryotes have either benefited from or endured polyploidy. Studies of polyploids soon after their formation have revealed genetic and epigenetic interactions between redundant genes. These interactions can be related to the phenotypes and evolutionary fates of polyploids. Here, I consider the advantages and challenges of polyploidy, and its evolutionary potential.

Polycomb silencing mechanisms and the management of genomic programmes.

Abstract: Polycomb group complexes, which are known to regulate homeotic genes, have now been found to control hundreds of other genes in mammals and insects. First believed to progressively assemble and package chromatin, they are now thought to be localized, but induce a methylation mark on histone H3 over a broad chromatin domain. Recent progress has changed our view of how these complexes are recruited, and how they affect chromatin and repress gene activity. Polycomb complexes function as global enforcers of epigenetically repressed states, balanced by an antagonistic state that is mediated by Trithorax. These epigenetic states must be reprogrammed when cells become committed to differentiation.