Structural organization of transposable element mdg4 fromDrosophila melanogaslerand a nucleotide sequence of its long terminal repeats

Abstract

A mobile dispersed genetic element, mdg4 , approximately 7.5 kilobases (kb) long has been cloned from D. melanogaster genome. Chromosomal bands have only few sites of mdg4 , but it always hybridizes to the chromocenter. The location of mdg4 varies among D. melanogaster strains. Blot hybridization shows that, in contrast to other mdg elements, mdg4 sequences are rather heterogeneous. Only few copies are full-length. A strong amplification of mdg4 has occurred during the in vitro cultivation of cells involving only one mdg4 variant. Long terminal repeats (LTRs) and flanking sequences have been sequenced in two cloned copies of transposable element mdg4 . In both cloned copies of mdg4 , LTRs have an identical nucleotide sequence 479 bp long. The mdg4 is flanked by four-base-pair direct repeats, short mismatched palindromes being present at the ends of each LTR. The termini of the mdg4 body contain an oligopurine stretch and a region partially complementary to D. melanogaster tRNA-Lys. Thus, structural organization of mdg4 LTRs is similar to that of several other mdg elements and retroviral proviruses.

Mobile genetic elements in animal cells and their biological significance

“…melanogaster genome, only one or a few copies of mdg4 contain an additional HindIII site in the central part of the element as follows from Southern blotting and cloning experiments [36]. The copy number of mdg4 remained low (15-20 copies) in the D line of culture cells until the 70th passage.…”

“…The nucleotide sequences of LTRs have been determined for a number of mdg elements: mdg3 [31], copia [32], mdgl [33], mdg2 or Dm412 [34], Dm 297 and 17.6 [30], El04 [35], and mdg4, or gypsy [36]. All of them have many features in common (Fig.…”

Transposable elements P and gypsy in natural populations of Drosophila willistoni

“…The transposable elements (TEs) P and gypsy are some of the best-known mobile sequences in Drosophila melanogaster and are widely represented in the repetitive portion of the Drosophila genome, appearing to be resident members of the genome of several species (Bayev et al, 1984;Daniels and Strausbaugh, 1986;Stacey et al, 1986;Daniels et al, 1990;Loreto et al, 1998a, b). These elements are members of two large groups of mobile sequences (Finnegan, 1989) represented by Class I retrotransposons such as gypsy and 412 which use an intermediary RNA molecule and a reverse transcriptase to transpose and Class II DNA transposons such as the P and hobo transposons which use a transposase to mobilize.…”

“…The gypsy element is a long 7.3 kb retrotransposon containing 0.5 kb of well-conserved long terminal repeats (LTRs) and is widely distributed in Drosophila and the subgenus Sophophora (Stacey et al, 1986;Loreto et al, 1998b), the retroviral properties of gypsy probably explaining this wide distribution (Bayev et al, 1984;Terzian et al, 2000;Vázquez-Manrique et al, 2000;Mejlumian et al, 2002;Pélisson et al, 2002;Heredia et al, 2004). The strong pattern similarity between gypsy strains found by Bayev et al (1984) using Southern blotting suggests that this element invaded the D. melanogaster genome early in the evolutionary history of this species, the same appearing to be true for Drosophila simulans (Loreto et al, 1998b).…”

Gypsy transposition correlates with the production of a retroviral envelope-like protein under the tissue-specific control of the Drosophila flamenco gene

“…Its structure is very similar to that of retroviral proviruses ( Figure IA). Its sequence is organized as a central coding region flanked by two long terminal repeats (LTRs) (Bayev et al, 1984;Freund and Meselson, 1984;Marlor et al, 1986). Gypsy LTRs contain the initiation and termination signals necessary for the production of a terminally redundant genomic RNA (Arkhipova et al, 1986), and are flanked by the tRNA primer binding site and the purine-rich sequence necessary for initiation of DNA synthesis.…”