Kao S Y, Calman A F, Luciw P A, Peterlin B M
Howard Hughes Medical Institute, Department of Medicine, University of California, San Francisco 94143.
Nature. 1987;330(6147):489-93. doi: 10.1038/330489a0.
Human immunodeficiency virus-1 (HIV-1) gene expression is controlled by cellular transcription factors and by virally encoded trans-activation proteins of the HIV-1 tat and art/trs genes, which are essential for viral replication. Tat trans-activates HIV-1 gene expression by interacting with the trans-acting response element (TAR) located within the HIV-1 long terminal repeat (LTR) (ref. 2). In transient expression assays, tat mediates its effects largely by increasing the steady-state levels of messenger RNA species that contain the TAR sequence at or near their 5' ends, suggesting a function for tat either in transcription or in subsequent RNA processing. The tat gene could also facilitate translation of mRNA containing the TAR sequence. To determine the mechanism of trans-activation by tat, we analysed the structure and rate of synthesis of RNA species directed by the HIV-1 LTR in transient expression assays both in the presence and absence of tat. Although the rate of HIV-1 transcription initiation was not affected by tat, transcriptional elongation beyond position +59 was seen only in the presence of tat. Thus, tat trans-activates HIV-1 transcription by relieving a specific block to transcriptional elongation within the TAR sequence.
人类免疫缺陷病毒1型（HIV-1）的基因表达受细胞转录因子以及HIV-1 tat和art/trs基因的病毒编码反式激活蛋白的控制，这些蛋白对病毒复制至关重要。Tat通过与位于HIV-1长末端重复序列（LTR）内的反式作用应答元件（TAR）相互作用来反式激活HIV-1基因表达（参考文献2）。在瞬时表达试验中，tat主要通过提高5'端或其附近含有TAR序列的信使RNA种类的稳态水平来介导其作用，这表明tat在转录或后续RNA加工中发挥作用。tat基因也可能促进含有TAR序列的mRNA的翻译。为了确定tat反式激活的机制，我们在有和没有tat的情况下，通过瞬时表达试验分析了HIV-1 LTR指导的RNA种类的结构和合成速率。虽然HIV-1转录起始速率不受tat影响，但只有在有tat的情况下才能看到转录延伸超过+59位。因此，tat通过解除TAR序列内转录延伸的特定阻滞来反式激活HIV-1转录。
