Janetzky B, Lehle L
Institut für Zellbiologie, Universität Regensburg, Germany.
J Biol Chem. 1992 Oct 5;267(28):19798-805.
We have isolated and sequenced a genomic clone from Saccharomyces cerevisiae that shows structural features of a novel retrotransposon, designated Ty4. The element is 6.2 kilobases in length, and its genetic organization of the deduced functional domains is similar to Ty1 and Ty2 and thus different from Ty3. In contrast to hitherto known Ty elements from yeast, Ty4 is flanked by long terminal tau-element repeats instead of delta or sigma sequences. Ty4 contains two overlapping open reading frames. The first open reading frame, TYA4, is 1230 base pairs long and encodes a protein with a motif found in the nucleic acid-binding gag-protein of retroviruses. The second 4395-base pair open reading frame, TYB4, encodes a polyprotein that has domains with significant homology to retroviral protease, integrase, reverse transcriptase, and RNase H, structurally arranged in that order. The deduced amino acid sequence shows the greatest similarity with Ty2 and Ty1. The overall identity of the deduced functional protein domains is 28% with Ty2, 25% with Ty1, 19% with copia from Drosophila, and 18% with Ty3. Examination of genomic DNA from several laboratory strains indicates that Ty4 is present in two to four copies. Ty4 mRNA is of low abundance as compared to other Ty retrotransposons. At the 3' end of Ty4, two "solo" delta-elements, a full length and an overlapping, truncated one, are associated.
我们从酿酒酵母中分离并测序了一个基因组克隆，它展示出一种新型反转录转座子的结构特征，命名为Ty4。该元件长度为6.2千碱基，其推导的功能域的基因组织与Ty1和Ty2相似，因此与Ty3不同。与酵母中迄今已知的Ty元件相反，Ty4两侧是长末端tau元件重复序列，而非delta或sigma序列。Ty4包含两个重叠的开放阅读框。第一个开放阅读框TYA4长1230个碱基对，编码一种具有在逆转录病毒核酸结合gag蛋白中发现的基序的蛋白质。第二个4395个碱基对的开放阅读框TYB4编码一种多蛋白，该多蛋白具有与逆转录病毒蛋白酶、整合酶、逆转录酶和核糖核酸酶H有显著同源性的结构域，其结构按此顺序排列。推导的氨基酸序列与Ty2和Ty1的相似性最高。推导的功能蛋白结构域与Ty2的总体一致性为28%，与Ty1的为25%，与果蝇的copia为19%，与Ty3的为18%。对几个实验室菌株的基因组DNA检查表明，Ty4以两到四个拷贝存在。与其他Ty反转录转座子相比，Ty4 mRNA的丰度较低。在Ty4的3'端，有两个“单独”的delta元件，一个全长的和一个重叠的截短元件与之相关。
