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At least 19 recordsLinked to original sources
PubMed1985

A selective screen for transposable element mobilization in Drosophila melanogaster.

A selective system is described that provides a simple and sensitive assay for the detection and analysis of induced mobile element transpositions in Drosophila melanogaster. The system will detect a single event in samples greater than 10(6) and thus provides a eucaryotic assay system for monitoring the induction of transposition by a variety of agents including, but not limited to, chemical carcinogens and toxins, ionizing radiation, and various environmental pollutants. The experimental system focuses on an X-linked rosy+ transposon and a conditional lethal system that permits the detection of a single transposition event in very large samples. The results of a pilot experiment utilizing this system are presented.

Animals↗
PubMed1990

[Mobile elements in Drosophila natural populations in Azerbaijan].

The distribution of four genome DNA fragments containing different mobile elements in chromosomes of Drosophila melanogaster individuals from Azerbaijan coast and mountain populations was studied. The average copy number of each element was shown to be approx. equal in both populations. Sites of preferential localization, where the elements were present in no less than in half of individuals could be revealed in each population for all the elements. A part of these sites coincided with regions of intercalary heterochromatin, the number of such coincidences being larger in mountain populations. The copy number of the mobile elements under study in X-chromosomes of individuals from natural populations as well as from laboratory strains was less than in autosomes. X-chromosomes of different individuals differed in mobile elements' localization more than autosomes. It was assumed that peculiarities of mobile elements' distribution in X-chromosome could reflect the effect of decondensed structure of chromatin in male X-chromosome on the transposition of mobile elements.

Animals↗
PubMed1990

Evidence for horizontal transmission of the mobile element jockey between distant Drosophila species.

We addressed the possibility of the horizontal transfer of long interspersed element (LINE)-like mobile elements by studying the distribution of the Drosophila melanogaster LINE-like element jockey in different Drosophila species. Outside the D. melanogaster group jockey was detected only in the distantly related species Drosophila funebris. Cloning and sequencing of this element from D. funebris revealed the existence of the two open reading frames highly similar to those of jockey from D. melanogaster. Elements from both species are transcriptionally active and contain in their promoter regions a conserved sequence important for its activity. The high degree of similarity between the D. melanogaster and the D. funebris jockey and the absence of jockey from other sibling species of the D. funebris group provide evidence for the horizontal transmission of jockey into D. funebris.

Amino Acid Sequence↗
PubMed1988

Mdg-1 mobile element polymorphism in selected Drosophila melanogaster populations.

The changes in mdg-1 mobile element polymorphism that followed artificial selection for either high or low egg-to-adult viability in a Drosophila melanogaster population were investigated. The two selected subpopulations were thus characterized for fecundity, wing length, and number and location of the mdg-1 mobile element by in situ hybridization of the biotinylated--DNA on salivary gland chromosomes. The selected populations that differed greatly in egg-to-adult viability showed the same mean fecundity and identical values for intra and inter components of variances, intraclass correlation coefficient, and fluctuating asymmetry estimated on the wing length measurement. This indicates a non-correlated effect between deleterious mutations affecting viability and other fitness components. However, the two selected populations differed in their pattern of mdg-1 location, although the mean number of insertions per genome was not different from that of the initial population; hence, the number of insertions of the mdg-1 mobile element was independent of the effective population size. These results suggest that the mdg-1 copy number was regulated, and that during the selection process, drift and inbreeding made up new insertion patterns of the mdg-1 element in the selected populations. The results are discussed in the light of some recent theoretical models of the population dynamics of transposable elements.

Animals↗
PubMed1990

Mobile element insertions causing mutations in the Drosophila suppressor of sable locus occur in DNase I hypersensitive subregions of 5'-transcribed nontranslated sequences.

The locations of 16 mobile element insertions causing mutations at the Drosophila suppressor of sable [su(s)] locus were determined by restriction mapping and DNA sequencing of the junction sites. The transposons causing the mutations are: P element (5 alleles), gypsy (3 alleles), 17.6, HMS Beagle, springer, Delta 88, prygun, Stalker, and a new mobile element which was named roamer (2 alleles). Four P element insertions occur in 5' nontranslated leader sequences, while the fifth P element and all 11 non-P elements inserted into the 2053 nucleotide, 5'-most intron that is spliced from the 5' nontranslated leader approximately 100 nucleotides upstream of the translation start. Fifteen of the 16 mobile elements inserted within a approximately 1900 nucleotide region that contains seven 100-200-nucleotide long DNase I-hypersensitive subregions that alternate with DNase I-resistant intervals of similar lengths. The locations of these 15 insertion sites correlate well with the roughly estimated locations of five of the DNase I-hypersensitive subregions. These findings suggest that the features of chromatin structure that accompany gene activation may also make the DNA susceptible to insertion of mobile elements.

Animals↗
PubMed1986

Distribution and conservation of mobile elements in the genus Drosophila.

Essentially nothing is known of the origin, mode of transmission, and evolution of mobile elements within the genus Drosophila. To better understand the evolutionary history of these mobile elements, we examined the distribution and conservation of homologues to the P, I, gypsy, copia, and F elements in 34 Drosophila species from three subgenera. Probes specific for each element were prepared from D. melanogaster and hybridized to genomic DNA. Filters were washed under conditions of increasing stringency to estimate the similarity between D. melanogaster sequences and their homologues in other species. The I element homologues show the most limited distribution of all elements tested, being restricted to the melanogaster species group. The P elements are found in many members of the subgenus Sophophora but, with the notable exception of D. nasuta, are not found in the other two subgenera. Copia-, gypsy-, and F-element homologues are widespread in the genus, but their similarity to the D. melanogaster probe differs markedly between species. The distribution of copia and P elements and the conservation of the gypsy and P elements is inconsistent with a model that postulates a single ancient origin for each type of element followed by mating-dependent transmission. The data can be explained by horizontal transmission of mobile elements between reproductively isolated species.

Animals↗
PubMed1991

Transposition of mobile elements gypsy (mdg4) and hobo in germ-line and somatic cells of a genetically unstable mutator strain of Drosophila melanogaster.

Using the in situ hybridization technique, we have analysed the distribution of mobile elements in the X chromosomes of male offspring of individual mutator strain (MS) males crossed to attached-X females. The experiments demonstrate varying cytological localization of the mobile elements gypsy (mdg4) and hobo among different individuals. The other mobile elements investigated (mdg1, mdg3, 412, 297, copia, 17.6, Doc, H. M. S. Beagle, Springer, FB) display no changes in insertion sites. Such an experiment is equivalent to analysis of separate gametes of an MS individual. Thus, the ability of gypsy and hobo to transpose in germ-line cells is demonstrated directly. Transpositions occur at premeiotic stages of germ cell development, since they appear in clusters. Analysis of gypsy and hobo transposition events shows that they occur independently. The same experiment demonstrates that gypsy localization varies significantly between different salivary gland cells of an MS individual. Two types of gypsy hybridization sites can be distinguished: "permanent" sites, common to all cells, and "additional" ones varying between neighbouring salivary gland cells. These additional sites indicate gypsy transposition in somatic cells of the MS. Transposition of the hobo element in somatic cells has also been observed.

Animals↗
PubMed1989

[Localization in the body of the mobile element MDG1 of 2 regions specifically binding with Drosophila nuclear proteins].

Two regions in mdg1 mobile element's body can specifically bind nuclear proteins of Drosophila melanogaster, as demonstrated by the method of retention of DNA-protein complexes of nitrocellulose filters. The first region is situated in the 5'-end part of mdg1, 1 kb downstream the site of initiation of transcription and contains long oligo (A) blocks (from 14 to 30 nucleotides) in the coding chain. The second region is localized near the 3'-LTR and consists of tandem 14-nucleotide repeats and a palindrome, destruction of which leads to weaker binding. There is no competition between the two regions for proteins, which evidence that they are recognized by the different proteins. The binding with the first region can be suppressed by adding the 412 mobile element DNA. These regions are supposed to take place in the regulation of mdg1 transcription.

Animals↗
PubMed2026

Mobile elements in pituitary neuroendocrine tumors: integrative evidence and future directions.

Mobile genetic elements (MGEs), including LINE-1 retrotransposons, Alu and SVA elements, and human endogenous retroviruses (HERVs), constitute nearly half of the human genome and are increasingly understood to influence multiple dimensions of cancer evolution. Yet, pituitary neuroendocrine tumors (PitNETs) remain almost absent from mobilome research, despite exhibiting genomic and epigenetic contexts permissive to retroelement activation. In this review, we synthesize current evidence linking MGEs to PitNET biology and delineate unresolved but testable mechanisms. Structural genomic studies demonstrate that Alu-mediated non-allelic homologous recombination contributes to germline mutagenesis in MEN1 and AIP, reinforcing the notion that repetitive DNA architecture shapes PitNET predisposition. Transcriptomic analyses reveal global derepression of transposable elements and LINE-1 hypomethylation in subsets of tumors, while mechanistic connections to chromatin instability emerge from recurrent ATRX/DAXX deficiency and TP53 inactivation, both established repressors of retroelements. Furthermore, the retrocopy-derived long non-coding RNA RPSAP52 exemplifies how mobilome-origin transcripts can be co-opted as oncogenic regulators in PitNETs, acting through HMGA2-dependent proliferative networks. Preliminary data also suggest endogenous retroviral activation, with consistent upregulation of HERV envelope genes across distinct tumor subtypes. Nevertheless, no study has yet systematically mapped somatic mobile-element insertions (MEIs), quantified LINE-1 protein activity, or profiled HERV expression at locus resolution in PitNETs. Mobilome biology represents a tractable and conceptually rich frontier with diagnostic, prognostic, and therapeutic potential in pituitary tumorigenesis.

Humans↗
PubMed1992

[Insertion of the Doc mobile element into Drosophila satellite DNA].

Eight plasmids containing the satellite DNA of Drosophila melanogaster, density of 1,688 g/cm3, and DNA neighbouring sequences were selected from gene cosmid library. The Doc mobile element appeared to be present in three cosmids, together with the satellite DNA. Two Doc copies in the opposite orientations are present in one of these cosmids. One monomer of the satellite DNA is located between their 3'-ends, which indicates selectivity of the mobile element insertion into the monomer of this satellite DNA.

Animals↗
PubMed1989

Heat shocks do not mobilize mobile elements in genomes of Drosophila melanogaster inbred lines.

Males of three inbred lines of Drosophila melanogaster were heat-shocked 90 min at 37 degrees C. The progenies from treated and untreated males mated with untreated females of the same line were checked for their chromosomal insertion patterns of various mobile elements by either in situ hybridization or Southern blots. No modification in the pattern of insertion of the elements studied was observed after heat treatment. Hence, heating males of our inbred lines did not mobilize mobile elements, contrary to recent reports on other lines of Drosophila melanogaster.

Animals↗
PubMed1991

Cloning and analysis of the mobile element gypsy from D. virilis.

The homologue of the Drosophila melanogaster mobile element gypsy was cloned from the distantly related species D. virilis. It has three ORFs highly homologous to those of the element from D. melanogaster. gypsy from D. virilis appears to be actively transcribed and is capable of transposition. Comparison of the untranslated regions of both elements revealed conserved sequences including those which had previously been demonstrated to be important in transcription regulation. Distribution of gypsy among the different strains of D. virilis and different species within the D. virilis group was analyzed. Possible involvement of horizontal transmission in the process of spreading and evolution of gypsy is discussed.

Animals↗
PubMed1989

Mobile elements and transposition events in the cut locus of Drosophila melanogaster.

We have cloned from the Oregon R strain of Drosophila melanogaster a 240 kb segment of DNA that contains the cut (ct) locus, and characterized the region for the presence of repetitive elements. Within this region at least five copies of the suffix element were detected, as well as several putatively novel mobile elements. A number of mutations obtained from the unstable ctMR2 strain and its derivatives were mapped within the cut locus. Comparison between parental and daughter strains indicates that frequently two or more independent transposition events involving the cut locus occur simultaneously within a single germ cell, thus providing a molecular basis for the transposition explosion phenomenon.

Alleles↗
PubMed1990

[Hoppel-family of mobile elements of Drosophila melanogaster, flanked by short inverted repeats and having preferential localization in the heterochromatin regions of the genome].

A mobile element (ME) having 91% homology with Dm1360 (Kholodilov et al., 1987) has been cloned from the Drosophila melanogaster genome and sequenced. The family of ME was designated hoppel. The members of this family are flanked by short inverted repeats likewise P, hobo and HB. The hoppel is hybridized with 10-30 euchromatic sites of polytene chromosomes of different Drosophila stocks. Abundant hybridization with heterochromatic regions of chromosomes-chromocenter, pericentric heterochromatin, the 4 chromosome and telomeres was observed in all stocks of D. melanogaster examined and in D. simulans. At least six genomic variants of ME differing in length of the central part were revealed. Hoppel possesses ARS activity similar to the P element. Two ME hoppel were shown to be arranged as a direct repeat in the recombinant phage.

Animals↗
PubMed1986

[Interaction of mobile elements P and mdg3 in Drosophila melanogaster: genetic aspects].

It was found earlier that two unstable sn mutants isolated from natural populations are connected with insertion of mobile element mdg3 into the 7D1-2 region where singed gene (1-21.0) is localised. From two original sn mutants, a series of unstable sn alleles, both mutant and normal for phenotype, was extracted. Then we studied, how they change the mutation rate in germinal and somatic cells of different hybrids with pi 2 stock having P cytotype and active P elements in the chromosomes. Addition of P chromosomes, independently of the background of cytoplasm, proved to reduce the sn instability. The level of sn mutability was decreased with increasing the dose of P chromosomes. It is suggested that mutation events are caused by transposition of mdg3 and that both mdg3 and P elements compete for the same cellular factor, capable of activation of transposition process.

Alleles↗
PubMed1988

[Effect of the mobile element jockey on the suppression of insertion mutations in the cut locus of Drosophila melanogaster].

The data are reported on suppression of mutations at the cut locus induced by a mdg4 insertion carrying the other mobile element, "jockey". All mutations containing mdg4 with the jockey (ctMRpN) are suppressed by a classic suppressor su(Hw)2 and two new alleles obtained in this work. The extent of suppression increases, depending on the orientation of the jockey in mdg4 up to the point, when su(Hw) alleles known as recessive become semi-dominant. The jockey and mdg4 have been also found to influence the locus transcription in the norm and in case of suppression.

Alleles↗
PubMed1990

Autonomous transposition of gypsy mobile elements and genetic instability in Drosophila melanogaster.

The laboratory mutator strain (MS) of Drosophila melanogaster is characterized by an elevated frequency of spontaneous mutation (10(-3)-10(-4). Mutations occur in both sexes at premeiotic stages of germ cell development. The increased mutability is a characteristic feature of MS itself, since it appears in the absence of outcrossing. Most of the mutations arising in this strain are unstable: reversions to wild type, high frequency mutation to new mutant states and replicating instability were observed. We have investigated the localization of the transposable genetic elements mdg1, 412, mdg3, gypsy (mdg4), copia and P in the X chromosomes of the MS and in the mutant lines y, ct, sbt derived from it by in situ hybridization. The P element was not found in any of these strains. The distributions of mdg1, 412, mdg3 and copia were identical in the X chromosomes of the MS and its derivatives. However, the sites of hybridization with gypsy differ in the various lines tested. In the polytene chromosomes of MS animals significant variation in location and number of copies of the gypsy element was demonstrated between different larvae; copy numbers as high as 30-40 were observed. These results suggest autonomous transposition of gypsy in the MS genome while several other mobile elements remain stable.

Animals↗
PubMed1989

[Genetic instability and transposition of mobile element mdg4 in a mutator strain of Drosophila melanogaster].

Laboratory mutator strain of Drosophila melanogaster is characterized by increased (up to 10(-3)-10(-4) frequency of spontaneous mutability. Mutations appear in premeiotic stages of gametes development. The majority of mutations were unstable (high frequencies of reversions, appearance of new mutations at the same and other loci, replicating instability). Localization of mobile elements mdg1, mdg2, mdg3, mdg4, copia and P element in X chromosomes of mutator individuals and its mutations y, ct, sbt was studied by hybridization in situ. In all strains P element was absent. The distribution of mdg1, mdg2, mdg3 and copia was identical in mutator strains and its derivatives, but distribution of mdg4 was different. The essential heterogeneity in localization of mdg4 and increased (up to 30-40) copy number in the mutator strain individuals was observed. The ability of single element mdg4 to autonomous transpositions was thus shown.

Animals↗