Wu-Baer F, Lane W S, Gaynor R B
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75235-8594, USA.
J Mol Biol. 1998 Mar 27;277(2):179-97. doi: 10.1006/jmbi.1997.1601.
The transactivator protein Tat stimulates transcriptional elongation from the HIV-1 LTR. One mechanism by which Tat increases HIV-1 transcription is by interacting with RNA polymerase II and TFIIH to increase phosphorylation of the polymerase C-terminal domain. Recent studies indicate that specific elongation factors may also be required to modulate Tat function. Here, we used biochemical analysis and in vitro transcription assays to identify cellular factors required for Tat activation. This analysis resulted in the purification of a cellular factor Tat-CT1 which is a human homolog of the yeast transcription factor SPT5. Immunodepletion of Tat-CTl from HeLa extract demonstrated that this factor was involved in transcriptional activation by Tat. However, the absence of this factor from HeLa extract did not prevent transcriptional activation by VP16. These findings are consistent with a model in which Tat-mediated effects on transcriptional elongation are mediated in part by the action of the human homolog of the yeast transcription factor SPT5.
反式激活蛋白Tat刺激HIV-1长末端重复序列（LTR）的转录延伸。Tat增加HIV-1转录的一种机制是通过与RNA聚合酶II和TFIIH相互作用，以增加聚合酶C末端结构域的磷酸化。最近的研究表明，可能还需要特定的延伸因子来调节Tat功能。在这里，我们使用生化分析和体外转录试验来鉴定Tat激活所需的细胞因子。该分析导致纯化出一种细胞因子Tat-CT1，它是酵母转录因子SPT5的人类同源物。从HeLa提取物中免疫去除Tat-CT1表明该因子参与了Tat的转录激活。然而，HeLa提取物中缺乏该因子并不妨碍VP16的转录激活。这些发现与一种模型一致，即Tat对转录延伸的介导作用部分是由酵母转录因子SPT5的人类同源物的作用介导的。
