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PubMedDate not supplied

[The phenomenon of RNA interference and development of organism].

RNA interference consists in specific mRNA degradation in response to introduction of a double-stranded RNA, homologous in nucleotide sequence. RNA interference was found in eukaryotes and is used in genomics as a powerful method to determine the functions of genes with known nucleotide sequences. RNA interference is considered as a tool of protection against viruses and harmful consequences of mobile elements' transposals. The involvement of the components of RNA interference is considered in spermatogenesis of Drosophila melanogaster and regulation of the expression of genes in Caenorhabditis elegans responsible for temporal patterns of development. The role of RNQA interference in stem cell formation and functioning is also considered.

Animals↗
PubMed2003

[Retrotransposon MDG4 and its role in genetic instability of a mutator strain of Drosophila melanogaster].

This article summarizes the results of a ten-year study of genetic instability of a mutator strain of Drosophila melanogaster caused by transposition of the gypsy retrotransposon. The results of other authors working with an analogous system are analyzed. Possible mechanisms are suggested for the interaction of gypsy with the cell gene flamenco that participates in transposition control of this mobile element.

Animals↗
PubMed2003

Spread and survival of promiscuous IncP-1 plasmids.

Plasmids classified to the IncP-1 incompatibility group belong to the most stably maintained mobile elements among low copy number plasmids known to date. The remarkable persistence is achieved by various tightly controlled stability mechanisms like active partitioning, efficient conjugative transfer system, killing of plasmid-free segregants and multimer resolution. The unique feature of IncP-1 plasmids is the central control operon coding for global regulators which control the expression of genes involved in vegetative replication, stable maintenance and conjugative transfer. The multivalent regulatory network provides means for coordinated expression of all plasmid functions. The current state of knowledge about two fully sequenced plasmids RK2 and R751, representatives of the IncP-1alpha and IncP-1beta subgroups, is presented.

Bacterial Proteins↗
PubMed1992

[Interaction between the enhancers of yellow and the yellow gene in Drosophila melanogaster].

Earlier, mutations at six loci designated enhancers of yellow (e(y)1-6) were obtained in the system of prolonged instability, where transpositions of Stalker mobile element occur. These mutations decrease pigmentation of the cuticle in a number of alleles. In the present work, genetic analysis of the mechanism of action of e(y)1u1, e(y)3u1 and newly described e(y)7u1 mutations on the yellow locus expression was conducted. The data are obtained proving that the enhancers of yellow 1 and 3 control transcription of the yellow locus. At the same time, the interaction of here described gene e(y)7 with the yellow gene is likely to occur at the level of protein products.

Alleles↗
PubMedDate not supplied

[Conformational stimulation in DNA type macromolecules].

A concept for the description of structural elements mobility of a DNA-type macromolecule is suggested. The possible existence of conformational excitations weakly sensitive to a macromolecule heterogeneity in DNA is shown. The dependence of the macromolecule low-energy excitation spectrum on the nucleotide content is found and its sensitivity to thermal action is predicted.

DNA↗
PubMed2003

Evolution without speciation but with selection: LUCA, the Last Universal Common Ancestor in Gilbert's RNA world.

This is not an attempt to analyze the Last Universal Common Ancestor (LUCA) to understand the origin of living systems. We do not know what came before Gilberts' RNA world. Our analysis starts with the RNA world and with genes (biological replicators alla Dawkings) made up of RNA proteins with enzymatic catalytic functions within units that are not yet modern cells. We offer a scenario where cellular entities are very simple and without individuality; they are only simple primary units of selection (the first level of selection) in which replicators compete in the most Darwinian manner, totally deprived of cooperation and interactions among genes. The information processing system of this RNA world is inaccurate and inefficient when compared to that found in organisms that came later. Among the "genes" and the entities that harbor them, high mutation rate was the most prevalent source of variability and the only inheritance was through lateral gene transfer of mobile elements. There were no chromosomes or any other genomic organization. As millions of years accumulated, complex and organized biological structures and processes evolved thanks to the variability mustered up mostly by lateral gene transfers and mutations. With micro- and mini-satellites, lateral gene transfers became indispensable devices of selection to mold variability. Competition and Darwinian selection gave way to a new transition in evolution, one I consider ineluctable, in which cooperation among interactive genes prevailed for the sake of higher fitness. Compartmentalization constituted a major transition in evolution that spurted new types of genome organization. Minichromosomes is one of these; cellular membranes and cytoplasmic structures completed the picture of the primitive cell. However, the much talked about phylogenetic tree does not exit in that ancient LUCA. The tree has no organism at its base; only clusters of genes evoke a fragile beginning for the increasingly complex cell types that were to emerge later.

Animals↗
PubMed2004

[Integrons].

The development of antimicrobial resistance has led to the discovery of many natural mobile elements like transposons and conjugative plasmids. Integrons are carried on plasmids and transposons that potentially increase the dissemination of antibiotic resistance genes among bacterial species. Integrons are genetic elements containing the determinants of a site-specific recombination system. These DNA elements mediate the integration of antibiotic resistance genes into bacteria through the site-specific recombination. Integrons consist of an integrase gene (intl), a recombination site (attl), and one or two promoters responsible for expression of the inserted gene cassettes. Class 1 integrons are the most commonly studied and largely implicated type in the dissemination of antibiotic resistance among clinical isolates. In the last few years, a variety of new gene cassettes coding antibiotic resistance have been described. Having the ability of horizontal transfer of antibiotic resistance genes between interspecies of bacteria, integrons play a dominant role in the development of multiresistance in Enterobacteriaceae. In this review article, classification, structure and expression, epidemiology and clinical importance of integrons, has been discussed.

Drug Resistance, Bacterial↗
PubMedDate not supplied

[Heat shock proteins: functions and role in adaptation to hyperthermia].

The results are generalized of many-year studies into the adaptive role of heat shock proteins in different animals, including the representatives of cold- and warm-blooded species that inhabit regions with different thermal conditions. Adaptive evolution of the response to hyperthermia can lead to different results depending on the species. The thermal threshold of induction of the heat shock proteins in desert thermophylic species is, as a rule, higher than in the moderate climate species. In addition, thermoresistant species are often characterized by a certain level of heat shock proteins in cells even at a physiologically normal temperature. Although adaptation to hyperthermia is achieved in most cases without changes in the number of heat shock genes, they can be amplified in some cases in termophylic species. The role of mobile elements in evolution of the heat shock genes was shown and approach was developed for directional introduction of mutations in the promoter regions of these genes.

Adaptation, Physiological↗
PubMed1991

[A new approach to polygene mapping. Localization of genes, controlling the adaptation level of closely related lines of Drosophila melanogaster].

The phenomenon of hitch-hiking of dispersed mobile elements (molecular markers) is proposed as a new approach to polygene mapping. Retrotransposons MDG1 and copia are used as molecular markers to reveal chromosome 2 segments controlling high fitness level in Drosophila melanogaster. Comparison of closely related Drosophila melanogaster stocks with different fitness level demonstrates the role of pericentromeric region of chromosome 2 in the control of adaptive value.

Animals↗
PubMed2006

[Behavior of hobo and P transposons in yellow2-717 unstable line of Drosophila melanogaster and its derivatives after crossing with a laboratory strain].

Using fluorescent in situ hybridization technique (FISH), the frequency of hobo and P mobile elements transpositions on X chromosomes from the y2-717, isolated from the Uman' population of Drosophila melanogaster, as well as from its phenotypically normal and mutant derivatives, obtained as a result of crosses the males examined with the C(I)DX, ywf/Y females, was evaluated. It was demonstrated that the maximum frequency of hobo transpositions on X chromosomes of the males from derivative strains, subjected to repeated hobo-dysgenic crosses reached a value of 1.2 x 10(-2) per site per X chromosome per generation. The number of hobo copies in male X chromosomes from derivative strains was 3 times higher than in the original initial strain. Furthermore, the "old" hobo sites remained unchanged. In derivative strains, the frequency of hobo insertions was higher than that of excisions. One of the derivative strains, y1t-717alk3-2, was characterized by high intra-strain instability of hobo element localization. In the y2-717a1k3 and y1t-717alk3-2 strains a large inversion, In(1)1B; 13CD, was described. At the absence of the full-sized P element in the strains involved in crosses, maximum frequency of P element transpositions in the derivative strains reached a value of 1.2 x 10(-2) per site per X chromosome per generation.

Animals↗
PubMed2006

[Finding of Bov-B LINE retroelement in parthenogenetic and bisexual lizard species of the genus Darevskia (Lacertidae)].

The Bov-B LINE retrotransposon was first discovered in Ruminantia and was long considered to be specific for this order. Later, this mobile element was described in snakes and some lizard species. Analysis of phylogenetic relationships of Bov-B LINE elements from different ruminants, snakes, and lizard species led to the suggestion on horizontal transfer of this retrotransposon from Squamata to Ruminantia. In the Squamata group, Bov-B LINE element was found in all snakes and some lizard species examined. The element was not detected in the genomes of some species of the genera Lacerta and Podarcis. In the present study, using PCR amplification and sequencing of PCR products, Bov-B LINE element was identified in the genomes of parthenogenetic and bisexual species of the genus Darevskia (Lacertidae), as well as in such species as Lacerta agilis and Zootoca vivipara, where this retrotransposon had not been not detected before.

Animals↗
PubMed2006

[Origin, evolution, and migration of drug resistance genes].

Current views on the mechanisms responsible for the emergence of multiple drug resistance in clinical bacterial isolates are considered. Hypotheses on the origin of resistance genes derived from determinants of actinomycetes, antibiotic producers, and chromosomal genes of bacteria involved in cellular metabolism are reviewed. The mechanisms underlying the diffusion of resistance determinants by means of bacterial mobile elements (plasmids, transposons, and integrons) are discussed. Examples of the horizontal transfer of resistance determinants between Gram-positive and Gram-negative bacteria are presented.

Amino Acid Sequence↗
PubMed2006

[Bacterial superintegrons, a source of new genes with adaptive functions].

Data on the structural organization of the platform of integrons, gene cassettes, and integrons with integrated cassettes of genes encoding drug resistance are briefly summarized. Data obtained during recent years about superintegrons or chromosomal integrons, characteristics of their organization, the presence of genes with known adaptive and unidentified functions in them, as well as data on the differences between superintegrons and previously described multiple resistance integrons, are considered in more detail. Studies that provide evidence for translocations of gene cassettes from stationary chromosomal integrons into integrons associated with mobile elements resulting in gene flows in natural bacterial populations, which favors their survival and adaptation to changing environment, are also reviewed.

Adaptation, Biological↗
PubMed1991

[Non-random distribution of spontaneous and high temperature-induced recessive lethal mutations in the X-chromosome of Drosophila].

Frequency and localization of spontaneous and induced by high temperature (37 degrees C) recessive lethal mutations in X-chromosome of females belonging to the 1(1) ts 403 strain defective in synthesis of heat-shock proteins (HSP) were studied. No differences in frequencies of both spontaneous and induced lethals between 1(1) ts 403 and control strain were found, thus implying that the disturbances in HSP synthesis have no effect on this process in oocytes of Drosophila melanogaster females. Surprisingly, distribution of spontaneous and induced lethals along the X-chromosome of 1(1) ts 403 strain appeared to be non-random: they primarily are located in its distal portion (1-44 cM of genetic map or in I-II sections of the Bridges cytogenetic map). This correlates with non-random distribution of mobile elements in the X-chromosome of D. melanogaster (Leibovich, 1990).

Animals↗
PubMed1990

[Features of the structural organization of the MDG1 retrotransposon of Drosophila, revealed during its sequencing].

The two long open reading frames (ORF1 and ORF2) have been identified in the primary structure of the full-length copy of mdg1 Drosophila retrotransposon by the sequence analysis. These two partially overlapping frames code for the necessary information for transposition through the reverse transcription mechanism. There are unusually long leader and terminal regions in mdg1. The leader area contains two small open reading frames. One of them includes the information of a polypeptide with the typical zinc-binding region. Long oligo (dA) sequences separate the small ORFs from each other and from the long ORFs. Considerable homology between the MDG1 and 412 mobile elements has been detected by comparative analysis of their sequences. The common ancestor of these two elements is postulated.

Amino Acid Sequence↗
PubMed1990

[Cloning and molecular analysis of retrotransposon mdg4 from two Drosophila melanogaster strains, differing in genetic instability].

The copies of mobile element mdg4 (gypsy) were cloned from two different D. melanogaster strains. The first strain (stable) is characterized by small number of mdg4 copies and their constant localization in chromosomes. The second strain (unstable), which was originated from the first one, is characterized by increased number of mdg4 copies and higher frequency of its transpositions. The two copies of mdg4, cloned from stable and unstable strains differ in their structure and represent two different types of mdg4. Southern blot-analysis of structural organization of mdg4 in these two strains showed, that in the stable strain there are mdg4 copies of one type, and in the unstable strain there are both, but only the mdg4 copies of another type were amplified. In was shown by transient-expression experiments, that in spite of the structural differences both types of mdg4 were able to be transcribed. Nevertheless, in flies of stable strain the mdg4 transcripts were not detected.

Animals↗
PubMed1991

[Thrombosis of mechanical heart valve prosthesis. Value of transesophageal echocardiography in the study of mitral valve prosthesis].

Forty-three consecutive patients with mechanical valve prostheses underwent transthoracic and transoesophageal echocardiography for suspected thrombolic prosthetic valve dysfunction. The results of these investigations were compared with those of cineradiography and the clinical outcome. The diagnosis of thrombosis was retained in 11 of the 43 patients (10 mitral and 1 aortic valve prostheses). The transthoracic Doppler echo was clearly abnormal in 6 of the 11 cases. Transoesophageal echo was of essential value in all cases but one, showing abnormal movement of the mobile element and/or a paraprosthetic thrombus. The cineradiography gave false negative results in 6 cases. In conclusion, these cases underline the undeniable value of transoesophageal echocardiography in occlusive or non-occlusive thrombosis of a mitral valve prosthesis. This investigation should be undertaken whenever there is the least suspicion of thrombosis of the prosthesis.

Adult↗
PubMed1990

[Study of valvular prostheses by Doppler echography].

Doppler echocardiography is a reliable non-invasive method of following up patients with prosthetic heart valves. Transthoracic M mode and two-dimensional echo allow evaluation of the movement of the mobile element of the prosthesis and of the size of the cardiac chambers. Doppler studies (transprosthetic pressure gradient, valve surface area, trans- and periprosthetic regurgitation) give an indication of the hemodynamic profile of the prosthesis. Transesophageal echocardiography is especially useful when there are abnormalities suggestive of prosthetic valve dysfunction (fever, systemic embolism, clinical symptoms, haemolysis...).

Aortic Valve↗