Bayev A A, Lyubomirskaya N V, Dzhumagaliev E B, Ananiev E V, Amiantova I G, Ilyin Y V
Nucleic Acids Res. 1984 Apr 25;12(8):3707-23. doi: 10.1093/nar/12.8.3707.
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.
一种长度约为7.5千碱基（kb）的可移动分散遗传元件mdg4已从黑腹果蝇基因组中克隆出来。染色体带中mdg4的位点很少，但它总是与染色中心杂交。mdg4的位置在不同的黑腹果蝇品系中有所不同。印迹杂交表明，与其他mdg元件不同，mdg4序列相当异质。只有少数拷贝是全长的。在仅涉及一种mdg4变体的细胞体外培养过程中，mdg4发生了强烈扩增。已对转座元件mdg4的两个克隆拷贝中的长末端重复序列（LTRs）和侧翼序列进行了测序。在mdg4的两个克隆拷贝中，LTRs具有相同的479 bp长的核苷酸序列。mdg4两侧是四碱基对直接重复序列，每个LTR的末端存在短的错配回文序列。mdg4主体的末端包含一段寡嘌呤序列和一个与黑腹果蝇tRNA-Lys部分互补的区域。因此，mdg4 LTRs的结构组织与其他几种mdg元件和逆转录病毒前病毒的结构组织相似。
