Long terminal repeats (LTRs) of two members of mdg1 family were sequenced. In the both cases, they are represented by perfect direct repeats 442 and 444 bp in length. Sixteen nucleotides in the LTRs of two different mdg1 elements are different. Each LTR contains slightly mismatched 16-nucleotide inverted repeats located at the ends of the LTR. Six base pairs closest to the termini of LTR form perfect inverted repeats. On the gene-distal sides of LTRs, short 4-nucleotide direct repeats are located, probably representing the duplication of a target DNA sequence arising from insertion of mdg. They are different in the two cases analyzed. Just as the other analyzed eukaryotic transposable elements, mdg1 starts with TGT and ends with ACA. Within the both strands of LTR, the sequences similar to Hogness box (a putative signal for RNA initiation, or a selector) and AATAAA blocks (putative polyadenylation signals) are present. The LTR of mdg1 contains many short direct and inverted repetitive sequences. These include a 10-nucleotide sequence forming a perfect direct repeat with the first ten nucleotides of the LTR. A region of LTR about 70 bp long is represented by simple repetitive sequences (TAT).
The whole-length mobile dispersed genetic element mdg1 has been cloned from D. melanogaster genome. It contains DNA fragments described earlier as Dm225 and Dm234, Mdg1 is 7.2 kb long and framed with two direct repeats of 300-400 base pairs each. Mdg1 family is represented by about 25 copies in the genome of flies and by 200 copies in the genome of cultured cell line 67J25D. Virtually all the copies in the genome of D. melanogaster have the same restriction map. Oligo(dA)-oligo(dT) regions were found within mdg1.
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