Leblanc P, Desset S, Dastugue B, Vaury C
Unité INSERM U384, Faculté de Médecine, Place Henri Dunant, 63000 Clermont-Ferrand, France.
EMBO J. 1997 Dec 15;16(24):7521-31. doi: 10.1093/emboj/16.24.7521.
ZAM, a new retroelement of Drosophila melanogaster, was identified as a mutational insertion at the white locus. It displays all the structural features of a vertebrate retrovirus. Its three open reading frames encode predicted products resembling the products of the gag, pol and env genes of retroviruses. Its transcription gives rise to an 8.6 kb full-length RNA and a 1.7 kb spliced message for the env gene. The latter encodes an envelope protein that is typical of elements having an extracellular phase of the life cycle. The identification of a ZAM envelope retrogene provides evidence that ZAM is mobilized through a reverse trancriptional process in the germ line of flies. We report that ZAM is distributed differently among D.melanogaster strains. Two stocks out of >15 tested display a ZAM high copy number, with numerous copies distributed on chromosomal arms. This high copy number is associated with a high transcriptional rate of ZAM. The existence of these two categories of strains offers a new genetic system in which the properties of a potential invertebrate retrovirus can be tested.
ZAM是黑腹果蝇的一种新型反转录元件，被鉴定为白色基因座处的突变插入。它具有脊椎动物逆转录病毒的所有结构特征。其三个开放阅读框编码的预测产物类似于逆转录病毒gag、pol和env基因的产物。其转录产生一个8.6 kb的全长RNA和一个用于env基因的1.7 kb剪接信使RNA。后者编码一种包膜蛋白，这是具有细胞外生命周期阶段的元件所特有的。ZAM包膜反转录基因的鉴定提供了证据，表明ZAM是通过果蝇生殖系中的逆转录过程进行移动的。我们报道ZAM在黑腹果蝇不同品系中的分布不同。在超过15个测试品系中，有两个品系显示出ZAM的高拷贝数，大量拷贝分布在染色体臂上。这种高拷贝数与ZAM的高转录率相关。这两类品系的存在提供了一个新的遗传系统，在其中可以测试潜在无脊椎动物逆转录病毒的特性。
