Berkhout B, Schoneveld I
University of Amsterdam, Department of Virology, Academic Medical Center, The Netherlands.
Nucleic Acids Res. 1993 Mar 11;21(5):1171-8. doi: 10.1093/nar/21.5.1171.
The initiation of reverse transcription of a retroviral RNA genome occurs by a tRNA primer bound near the 5' end of the genomic RNA at a position called the primer-binding site (PBS). To understand the molecular basis for this RNA-RNA interaction, the secondary structure of the leader RNA of the human immunodeficiency virus type 2 (HIV-2) RNA was analyzed. In vitro synthesized HIV-2 RNA was probed with various structure-specific enzymes and chemicals. A computer program was then used to predict the secondary structure consistent with these data. In addition, the nucleotide sequences of different HIV-2 isolates were used to screen for the occurrence of covariation among putative base pairs. The primary sequences have diverged rapidly in some HIV-2 isolates, however, some strikingly conserved secondary structure elements were identified. Most nucleotides in the leader region are involved in base pairing. An exception is the PBS sequence, of which 15 out of 18 nucleotides are exposed in an internal loop. These findings suggest that the overall structure of the HIV-2 genome has evolved to facilitate an optimal interaction with its tRNA primer.
逆转录病毒RNA基因组的逆转录起始是由一种与基因组RNA 5'端附近一个称为引物结合位点（PBS）的位置结合的tRNA引物引发的。为了理解这种RNA-RNA相互作用的分子基础，对人类免疫缺陷病毒2型（HIV-2）RNA的前导RNA二级结构进行了分析。用各种结构特异性酶和化学物质探测体外合成的HIV-2 RNA。然后使用计算机程序预测与这些数据一致的二级结构。此外，不同HIV-2分离株的核苷酸序列用于筛选假定碱基对之间的共变情况。在一些HIV-2分离株中，一级序列迅速分化，然而，仍鉴定出一些显著保守的二级结构元件。前导区的大多数核苷酸参与碱基配对。一个例外是PBS序列，其18个核苷酸中有15个暴露于一个内环中。这些发现表明，HIV-2基因组的整体结构已经进化，以促进与它的tRNA引物的最佳相互作用。
