Awang G, Sen D
Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada.
Biochemistry. 1993 Oct 26;32(42):11453-7. doi: 10.1021/bi00093a024.
Retroviral genomes consist of two identical RNA molecules joined noncovalently near their 5' ends, at domains called dimerization linked sequences (DLS). This physical linkage of the genomic RNAs is considered important for the control of several steps in the viral life cycle, such as recombination, translation, and encapsidation. The putative DLS of human immunodeficiency virus-1 (HIV-1), a 111-nucleotide, purine-rich stretch of RNA, has been found necessary and sufficient for a salt-induced dimerization of the genome in vitro. Our investigation into the mechanism of this dimerization reveals sharply varying influences of the different alkali cations on both the formation and the stabilization of the dimer, a pattern closely related to that of telomeric G-DNA complexes. To probe this phenomenon, we have carried out experiments using short antisense DNA oligomers to define the segments of the DLS that are required for dimerization and methylation protection to implicate sets of guanines in forming Hoogsteen hydrogen bonds within the dimer. Cumulatively, these data provide further evidence for the existence of guanine quartets within the dimerized HIV-1 DLS. We propose models in which guanine quartets not only allow the homodimerization of HIV-1 and other retroviral genomic RNAs but also permit the two RNA strands in a dimer to exist in an overall parallel orientation, as has been observed by electron microscopy.
逆转录病毒基因组由两个相同的RNA分子组成，它们在靠近其5'端的称为二聚化连接序列（DLS）的结构域处通过非共价键连接。基因组RNA的这种物理连接被认为对控制病毒生命周期中的几个步骤很重要，例如重组、翻译和衣壳化。人类免疫缺陷病毒1型（HIV-1）的假定DLS是一段111个核苷酸、富含嘌呤的RNA片段，已发现在体外盐诱导的基因组二聚化中是必要且充分的。我们对这种二聚化机制的研究揭示了不同碱金属阳离子对二聚体形成和稳定的影响差异很大，这一模式与端粒G-DNA复合物的模式密切相关。为了探究这一现象，我们使用短反义DNA寡聚物进行了实验，以确定二聚化所需的DLS片段，并通过甲基化保护来暗示鸟嘌呤在二聚体内形成Hoogsteen氢键的情况。这些数据累积起来，为二聚化的HIV-1 DLS中存在鸟嘌呤四联体提供了进一步的证据。我们提出了一些模型，其中鸟嘌呤四联体不仅允许HIV-1和其他逆转录病毒基因组RNA的同源二聚化，还允许二聚体中的两条RNA链以整体平行的方向存在，这已通过电子显微镜观察到。
