Mathias S L, Scott A F, Kazazian H H, Boeke J D, Gabriel A
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Science. 1991 Dec 20;254(5039):1808-10. doi: 10.1126/science.1722352.
L1 elements are highly repeated mammalian DNA sequences whose structure suggests dispersal by retrotransposition. A consensus L1 element encodes a protein with sequence similarity to known reverse transcriptases. The second open reading frame from the human L1 element L1.2A was expressed as a fusion protein targeted to Ty1 virus-like particles in Saccharomyces cerevisiae and shown to have reverse transcriptase activity. This activity was eliminated by a missense mutation in the highly conserved amino acid motif Y/F-X-D-D. Thus, L1 represents a potential source of the reverse transcriptase activity necessary for dispersion of the many classes of mammalian retroelements.
L1元件是高度重复的哺乳动物DNA序列，其结构表明通过逆转座进行扩散。一个共有L1元件编码一种与已知逆转录酶具有序列相似性的蛋白质。来自人类L1元件L1.2A的第二个开放阅读框被表达为一种靶向酿酒酵母中Ty1病毒样颗粒的融合蛋白，并显示具有逆转录酶活性。这种活性被高度保守的氨基酸基序Y/F-X-D-D中的一个错义突变消除。因此，L1代表了许多类哺乳动物逆转元件扩散所需的逆转录酶活性的潜在来源。
