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S G Georgieva

Publications and source records attributed to S G Georgieva.

At least 19 recordsLinked to original sources
PubMed2005

[Study of the novel tissue-specific RNA polymerase II transcription factor].

It has been established that retrogenes lose introns and regulatory regions. Most of them become pseudogenes, but some acquire tissue-specific functions. In this study, a contrary situation is described, when a retrogene from Drosophila melanogaster performs the main functions and is expressed in all tissues, while the initial gene is active only in a small part of the male germ cells. It is suggested that this phenomenon resulted from retroposition of the initial precursor gene in the transcription-suitable region of the genome.

Animals↗
PubMed2005

[Transcriptional coactivator SAYP can suppress transcription in heterochromatin].

The new transcriptional coactivator SAYP binds at many sites to transcriptionally active chromatin of polytene chromosomes, colocalizes with RNA polymerase II, and coactivates transcription. On the other hand, SAYP is present in heterochromatic regions of chromosome IV and in the chromocenter and suppresses transcription of transgenes located in heterochromatin. The conserved SAY domain of SAYP is involved in transcription activation, while its PHD domains are responsible for gene silencing in heterochromatin. Thus, SAYP plays a dual role in regulating transcription in euchromatic and heterochromatic regions.

Animals↗
PubMed2003

[Use of a genetic system of the chimeric protein P-Ph in the repression of gene transcription of the leg-arista-wing complex in Drosophila].

Preliminary analysis of the leg-arista-wing complex (lawc) gene region in the corresponding mutants revealed P element insertion in the transcribed region of this locus. To demonstrate the main role of P element insertion in the complex pleiotropic phenotypic manifestation of the lawc gene, a system using P-Ph chimeric protein and based on the P-mediated repression of the lawc in vivo transcription was applied. As a result, extreme lawc-mutant phenotypes were obtained and examined. The P-Ph-mediated decrease of the level of the lawc gene transcription was also demonstrated.

Alleles↗
PubMed2001

Adjustment of transfer tools for the production of micro- and macroarrays.

A transfer tool adjustment procedure for the generation of micro- and macroarrays is described. It is based on control spotting of solutions containing radioactive or fluorescent labels and the quantification of each obtained spot by standard image-analyzing software. This method provides a simple, rapid, and efficient way to control the quality and liquid delivery properties of spotting transfer tools.

Biotechnology↗
PubMed2001

[Molecular characteristics of the new evolutionary-conserved nuclear protein e(y)2].

Molecular structural and function analyses of the Drosophila melanogaster enhancer of yellow 2 (e(y)2) gene showed that its product acts as a transcription factor and is one of the basic elements of the eukaryotic transcription system. The gene is expressed at all stages of D. melanogaster development and consists of a single intron coding for the protein of 101 amino acid residues. The e(y)2 protein does not contain regions homologous to known proteins. The protein binds with chromatin but not with DNA. On evidence of immune staining, e(y)2 occurs in the nuclei of all D. melanogaster cells. Each nucleus contains approximately 1.2 x 10(4) molecules of the protein. Immune staining revealed approximately 200 sites of e(y)2 location on polytene chromosomes. The protein is evolutionarily conserved: its homologs were found in evolutionary distant organisms, such as plants, mammals, and protozoans. Amino acid sequences of human, rabbit, and mouse e(y)2 are identical to each other.

Amino Acid Sequence↗
PubMed2001

[Nuclear protein e(y)2 from Drosophila melanogaster participates in transcription control].

Molecular analysis of a new evolutionarily conserved transcription factor, e(y)2, was carried out. The protein was detected in a complex of approximately 700 kDa contained in a Drosophila melanogaster transcription nuclear extract. The e(y)2 protein was shown to interact with components of the preinitiation transcription complex TFIID. Addition of e(y)2 to a transcription extract of HeLa cells increased transcription 4-5 times when chromatin, but not free DNA, was used as a template. Genetic analysis showed that the C-terminal amino acid residues of transcription factor TAFII40 are important for its interaction with e(y)2.

Animals↗
PubMed1991

[Induction of unstable mutations in Drosophila melanogaster by microinjection of oncogenic virus DNA into the embryo polar plasma. Insertional nature of mutations].

We have demonstrated that mutations induced in Drosophila melanogaster by the microinjections of adenovirus Sa7 DNA in early embryos are of insertional nature. The role of insertional elements is played by the Drosophila transposons, but not by the virus DNA. The ability of oncoviral DNA to induce transpositions of mobile elements in recipient genome is the molecular basis of this system of genetic instability.

Adenoviridae↗
PubMed1990

Mitomycin C induces genomic rearrangements involving transposable elements in Drosophila melanogaster.

Mitomycin C was injected into the abdomen of male flies of the y2 sc1 waG strain of Drosophila melanogaster. They were mated with females bearing attached-X chromosomes, and the male offspring (F1) were analysed for the appearance of mutations in the X chromosome. We observed y+ and sc+ reversions induced either by excision of mdg4 (gypsy) with retention of one long terminal repeat (LTR) or by insertion of a foreign sequence into mdg4, partial reversion of the waG mutation, waG----waGd, and unstable f mutations. The overall mutation frequency was considerably higher than in control flies of the y2 sc1 waG strain. Possible mechanisms of genomic rearrangements induced by Mitomycin C, in particular the role of homologous recombination, are discussed.

Animals↗
PubMed1990

[Transpositional bursts and chromosome rearrangements in unstable lines of Drosophila].

The phenomenon of transpositional bursts-massive simultaneous transpositions of mobile elements belonging to different structural classes and accompanied by multiple mutagenesis were earlier described. Although the mechanisms of this phenomenon are still unclear, it is obvious now that it embraces total genome and includes not only transpositions of different mobile elements but also recombination processes--homologous recombination for LTR's and gene conversion. It is shown in this work that transpositional bursts may be accompanied by appearance of grass chromosomal rearrangements. The chain of closely related mutations which is characterized, as well as pedigrees described earlier, by coordinated mutational transitions and multiple transpositions of mdg1, mdg2 and retrotransposon jokey was analyzed. Spontaneous appearance of mutations in the loci yellow, white (deficiency for 462 kb) and cut (insertion of mdg4, together with jokey) correlates with appearance of inversion In(I), 14A-20B, and the reversions of these mutations to the wild type (y+w+ct+) or to other alleles (ctMR2--insertion of mdg4 without jokey) are accompanied by reversions of inversion. The relationship of all lines analyzed in this work as well as the lines from other pedigrees was proved using analysis of polymorphic restriction sites at the scute and cut loci (5 probes were used). All "y w ctpN"--type mutants are shown to have insertion of about 7 kb at the scute locus which causes no alteration of phenotype. This once again proves multiple and coordinated character of changes taking place during hybrid dysgenesis.

Animals↗
PubMed1989

Mobile genetic elements in Drosophila melanogaster (recent experiments).

Recent data obtained in the authors' laboratories concerning the behaviour of mobile genetic elements of Drosophila melanogaster are reviewed. It was found that the mobile element jockey represents the typical LINE element. It is efficiently transcribed in D. melanogaster cells in flies and in culture. Transcription is initiated from the +1 nucleotide of jockey and depends on an internal promoter. This is the first case of an internal promoter being used by RNA polymerase II. Several events which take place during the transposition bursts in ctMR2 family of strains were described. Among them are the removal of mobile dispersed genetics (mdg) elements (with solo long terminal repeat (LTR) remaining at the site of excision), complete removal of an mdg element, and reinsertion of the same mdg to the same place either in the presence or in absence of solo LTR sequence. Finally, the formation of deletions was observed. A 462-bp deletion destroying the white locus can be further repaired (w+ reversion). Thus, transposition bursts include many different genetic events. A novel system of prolonged genome destabilization was described. It depends on mobilization of a new mobile element called Stalker. After certain crosses Stalker actively moves for dozens of generations giving rise to large numbers of insertion mutations. Several novel genes were detected using mobilized Stalker. They include a modifier of mdg4 and six enhancers of yellow mutations.

Animals↗
PubMed1988

jockey, a mobile Drosophila element similar to mammalian LINEs, is transcribed from the internal promoter by RNA polymerase II.

The mobile element jockey is similar in structural organization and coding potential to the LINEs of various organisms. As demonstrated here, two polyadenylated jockey transcripts detected at different stages of Drosophila ontogenesis and in cell cultures have the same length as genomic copies of jockey and correspond to the strand containing ORFs. alpha-amanitin experiments indicate that jockey is transcribed by RNA polymerase II. Analysis of both expression of CAT constructions and initiation of transcription in jockey genomic and transfected copies has shown that jockey transcription is controlled by an internal promoter. Inward location of the promoter allows it to be preserved in the course of replication via reverse transcription and accounts for the distribution of jockey and probably other LINEs throughout the genome. This is the first case of an internal promoter described for RNA polymerase II. The comparison of sequences at the beginning of LINE elements in Drosophila allows one to detect possible core sequences.

Animals↗
PubMed1988

[The Drosophila mobile element jockey, being a typical LINE, is transcribed from the internal promoter by RNA polymerase II].

Two polyadenylated transcripts of the jockey are detected at different stages of Drosophila melanogaster ontogenesis and in the cell culture. They have the same length as complete and deleted copies of jockey and correspond to the DNA strand containing open reading frames coding for polypeptides which are homologous to retroviral RNA-(DNA)-binding proteins and to their reverse transcriptases. The results of the experiments, where transcription was inhibited with alpha-amanitin in vivo, indicate that jockey is transcribed by RNA polymerase II. The analysis of expression of CAT constructions made on the basis of jockey, and the detection of a fixed site for transcription initiation in jockey genomic and transfected copies have shown that jockey transcription is controlled by an internal promoter located not farther than 12 nucleotides from the beginning of the element. Such an inward location of the promoter allows it to be preserved in replication via reverse transcription and accounts for the distribution of jockey and probably other LINEs throughout the genome. This is the case of the first internal promoter described for RNA polymerase II. The comparison of starting sequences of LINEs in Drosophila makes it possible to detect core sequences of such a promoter.

Amanitins↗