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PubMedDate not supplied

[A new class of mobile genetic elements of Drosophila melanogaster].

Clone Dm A89 was obtained upon cloning of DNA fragments coding abundant poly(A+)RNA's of D. melanogaster. Dm A89 was identified as a new transposable element using in situ hybridization with polytene chromosomes of two independent highly isogenic lines of D. melanogaster oregon RC and gt wa Dm A89 hybridizes with approximately 20 sites in each line. A portion of Dm A89 is homologous to the distal part of type I ribosomal gene insertion sequence and is highly repetitive. Two other sections of the clone have much less redundancy. The unity of the three fragments is not casual, as revealed by cloning of some other genomic sequences homologous to Dm A89. Dm A89 is actively transcribed throughout the development of D. melanogaster and produces polyadenylated RNA 1.1 kb long.

Animals↗
PubMed1987

[Plasmids and mobile genetic elements of pathogenic Yersinia bacteria].

The review of literature is devoted to molecular and genetic organization of movable genetic elements responsible for synthesis of pathogenicity factors of Yersinia bacteria. General characterization of Yersinia pathogenicity factors is given. We analysed the role of plasmids in expression of the pathogenic properties of these bacteria and the role of IS elements of Yersinia in expression of genes encoding synthesis of the pathogenicity factors. Replicative properties of Yersinia plasmids are described. The role of chromosomal genes in regulation of synthesis of the plasmid-specific pathogenicity factors is discussed.

DNA Transposable Elements↗
PubMedDate not supplied

[Directed transpositions in the genome of the mobile hobo element in a long-term selected strain of Drosophila melanogaster].

The object of our investigation was an inbred LA strain of Drosophila melanogaster. This strain was selected during more than 700 generations for low male mating activity and was characterized by complex abnormalities and the remarkably high level of spontaneous mutability. The last property is determined by hobo system of hybrid dysgenesis. LA strain's hobo activity potential in H-E system of hybrid dysgenesis comprise 30-40%. It may be drastically increased up to 70-80% through LA-strain chromosome isogenization in dysgenic crosses. In genomes of independent isogenic LA substrains, numerous directional transpositions of hobo element take place. In spite of it, the retention of hobo element insertion sites inherent in original LA persist. The obtained data open up a new possibilities to study the genome instability mechanisms.

Animals↗
PubMed1998

[New evidence for the induction of mobile genetic element transpositions by severe heat shock].

The induction of retrotransposon 412 transpositions by stress was studied in detail. Males of an isogenic line carrying the radius incompletus (ri) mutation of the Mendelian gene were exposed to heavy heat shock (HHS). The procedure consisted of treatment at 37 degrees C for 1 h and at 4 degrees C for 1 h, with reciprocal changes of developmental temperature 3 times, sequentially; the males were then crossed with untreated females. The same males were crossed both on the fifth and ninth day after the HHS treatment. On the basis of in situ hybridization in 85 F1 larvae, 193 transpositions were identified. After treatment, the transposition rate increased by two orders of magnitude (compared to control) and amounted to 0.11 events per site of the original isogenic line per spermium per generation. Two hot sites (segments) of preferential transposition localization, 43B and 97CD, were detected after the first cross; these sites comprised more than 3/4 of all transpositions. Sperm from the first cross were exposed to HHS during the time period of 120 to 244 h after the appearance of the corresponding germline cells, probably at the stage of spermatid maturation. The overinduction of transpositions was shown to occur in these sites and at this stage. In the remaining sites, after the first cross, and in all sites, after the second cross, the rate of induced transpositions was (1.3-3.1) x 10(-2) events per site per spermium per generation, which is higher than in the control by an order of magnitude. This basic induction level was observed at all stages of spermatogenesis. The induction of transposition by heavy heat shock may be considered established.

Animals↗
PubMed1986

Structure and genomic organization of proretrovirus-like elements partially eliminated from the somatic genome of Ascaris lumbricoides.

A clone containing a middle repetitive element next to satellite DNA has been isolated from a germ line genomic library of the chromatin eliminating nematode Ascaris lumbricoides var. suum. The structure of this element has been elucidated by comparison of several clones containing the element in different environments. It is flanked by 256-bp-long terminal repeats (LTRs) and has an internal region of approximately 7 kb. The nucleotide sequences of both the 5' and the 3' LTRs have been determined. The element has a strong structural similarity with retroviral proviruses and related mobile elements. It was therefore named 'Tas', for transposon-like element of Ascaris. Approximately 50 Tas copies are dispersed over approximately 20 different chromosomal sites. Their genomic distribution varies between individuals, indicating that Tas elements are mobile in the Ascaris genome. Two variant forms, Tas-1 and Tas-2, present in a ratio of approximately 2 to 1 in the germ line genome, have been characterized. They differ not only in their restriction pattern, but also in their elimination behaviour. While only about one-fourth of the Tas-1 elements are expelled from the somatic cell lineage, all Tas-2 copies are specifically eliminated and are thus confined to the germ line cells. We have demonstrated that a cloned representative of Tas-1 elements is expelled concomitantly with its flanking DNA sequences during the chromatin elimination process.

Animals↗