Gatignol A, Kumar A, Rabson A, Jeang K T
Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1989 Oct;86(20):7828-32. doi: 10.1073/pnas.86.20.7828.
Human immunodeficiency virus type 1 (HIV-1) trans-activator protein Tat activates the expression of its viral long terminal repeat (LTR) through a target transactivation-responsive element termed TAR. We have constructed cell lines that constitutively express the HIV-1 Tat protein. Analyses of nuclear proteins from these cells and from matched control cells that do not express Tat have identified three proteins that bind to a radiolabeled HIV-1 TAR RNA probe. These polypeptides are 100 kDa, 62 kDa, and 46 kDa in size. Competition experiments using a wild-type TAR RNA sequence, a biologically inactive mutant sequence of TAR, and an unrelated RNA species demonstrated that these proteins show higher binding affinity to wild-type TAR than to the other two non-trans-activatable sequences. We hypothesize that these cellular proteins may mediate a function necessary in Tat-dependent activation of the LTR. The fact that no differences were seen in the binding profiles of nuclear proteins to TAR RNA in Tat-producing and Tat-nonproducing cells suggests that Tat does not directly interact with TAR.
1型人类免疫缺陷病毒（HIV-1）反式激活蛋白Tat通过一个名为TAR的靶反式激活应答元件来激活其病毒长末端重复序列（LTR）的表达。我们构建了组成型表达HIV-1 Tat蛋白的细胞系。对这些细胞以及不表达Tat的匹配对照细胞的核蛋白进行分析，鉴定出了三种与放射性标记的HIV-1 TAR RNA探针结合的蛋白。这些多肽的大小分别为100 kDa、62 kDa和46 kDa。使用野生型TAR RNA序列、无生物学活性的TAR突变序列以及无关RNA物种进行的竞争实验表明，这些蛋白对野生型TAR的结合亲和力高于对其他两个不可反式激活序列的结合亲和力。我们推测这些细胞蛋白可能介导了Tat依赖性LTR激活中必需的一种功能。在产生Tat的细胞和不产生Tat的细胞中，核蛋白与TAR RNA的结合谱没有差异，这一事实表明Tat不会直接与TAR相互作用。
