Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland.
Reverse Transcriptase Biochemistry Section, HIV Drug Resistance Program, Frederick National Laboratory, Frederick, Maryland, USA.
Nat Struct Mol Biol. 2014 Apr;21(4):389-96. doi: 10.1038/nsmb.2785. Epub 2014 Mar 9.
Retrotransposons are a class of mobile genetic elements that replicate by converting their single-stranded RNA intermediate to double-stranded DNA through the combined DNA polymerase and ribonuclease H (RNase H) activities of the element-encoded reverse transcriptase (RT). Although a wealth of structural information is available for lentiviral and gammaretroviral RTs, equivalent studies on counterpart enzymes of long terminal repeat (LTR)-containing retrotransposons, from which they are evolutionarily derived, is lacking. In this study, we report the first crystal structure of a complex of RT from the Saccharomyces cerevisiae LTR retrotransposon Ty3 in the presence of its polypurine tract-containing RNA-DNA hybrid. In contrast to its retroviral counterparts, Ty3 RT adopts an asymmetric homodimeric architecture whose assembly is substrate dependent. Moreover, our structure and biochemical data suggest that the RNase H and DNA polymerase activities are contributed by individual subunits of the homodimer.
逆转录转座子是一类可移动的遗传元件，通过逆转录酶（RT）的 DNA 聚合酶和核糖核酸酶 H（RNase H）活性，将其单链 RNA 中间体转化为双链 DNA 进行复制。尽管已有大量关于慢病毒和γ逆转录病毒 RT 的结构信息，但缺乏对其进化起源的长末端重复（LTR）含有逆转录转座子的对应酶的等效研究。在这项研究中，我们报告了第一个含有多嘧啶片段的 RNA-DNA 杂交物的酿酒酵母 Ty3 LTR 逆转录转座子 RT 复合物的晶体结构。与逆转录病毒 RT 相比，Ty3 RT 采用不对称的同源二聚体结构，其组装依赖于底物。此外，我们的结构和生化数据表明，RNase H 和 DNA 聚合酶活性由同源二聚体的单个亚基贡献。
