Chowdhury M, Taylor J P, Tada H, Rappaport J, Wong-Staal F, Amini S, Khalili K
Department of Biochemistry and Molecular Biology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107-6799.
Oncogene. 1990 Dec;5(12):1737-42.
We compared the ability of HIV-1 tat protein and JCV T-antigen in inducing transcription from the JCV late promoter, JCVL. A JCVL promoter-chloramphenicol acetyltransferase plasmid (pJCL-CAT) was transfected into human glial cells alone or together with plasmids producing T-antigen and tat protein. CAT enzyme activity obtained from the transfected cells indicated that both JCV T-antigen and HIV-1 tat proteins stimulated JCV late gene expression. However, the level of induction mediated by tat protein was significantly higher than that obtained with T-antigen. Moreover, in contrast to JCV T-antigen, tat stimulated JCVL-promoter activity over a narrow range of ptat expressor plasmid concentration. Co-transfection of both T-antigen and tat plasmids at optimal concentrations resulted in greater than additive CAT activity from the JCVL promoter. This synergism suggests that the two activator proteins utilize alternative mechanisms to exert their effects. Using deletion mutations from the 5' end of the JCVL promoter, we demonstrated that different regions within the JCV enhancer/promoter are important for T-antigen and tat induction, implying that these activators function through distinct targets to increase JCVL promoter activity.
我们比较了HIV-1反式激活因子蛋白（tat蛋白）和多瘤病毒（JCV）T抗原诱导JCV晚期启动子（JCVL）转录的能力。将一个JCVL启动子-氯霉素乙酰转移酶质粒（pJCL-CAT）单独或与产生T抗原和tat蛋白的质粒一起转染到人神经胶质细胞中。从转染细胞获得的氯霉素乙酰转移酶（CAT）酶活性表明，JCV T抗原和HIV-1 tat蛋白均能刺激JCV晚期基因表达。然而，tat蛋白介导的诱导水平显著高于T抗原所获得的水平。此外，与JCV T抗原不同，tat在较窄的ptat表达质粒浓度范围内刺激JCVL启动子活性。以最佳浓度共转染T抗原和tat质粒会使JCVL启动子产生高于相加效应的CAT活性。这种协同作用表明这两种激活蛋白利用不同机制发挥作用。利用JCVL启动子5'端的缺失突变，我们证明JCV增强子/启动子内的不同区域对T抗原和tat的诱导很重要，这意味着这些激活因子通过不同靶点发挥作用以增加JCVL启动子活性。
