Goodrich J A, Hoey T, Thut C J, Admon A, Tjian R
Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Cell. 1993 Nov 5;75(3):519-30. doi: 10.1016/0092-8674(93)90386-5.
Enhancement of RNA polymerase II transcription by the viral transactivator VP16 requires the TFIID complex, which consists of the TATA-binding protein (TBP) and TBP-associated factors (TAFs). Here we report the molecular cloning, expression, and biochemical characterization of Drosophila TAFII40 (dTAFII40), a subunit of TFIID. In vitro protein-protein interaction assays revealed direct binding between dTAFII40 and a 39 amino acid VP16 activation domain. In addition, affinity chromatography indicated a direct binding of the basal factor TFIIB to immobilized dTAFII40. Since VP16 also binds TFIIB, our results suggest a ternary interaction among an activator, a coactivator, and a basal transcription factor. Antibodies directed against dTAFII40 inhibited activation by GAL4-VP16 without affecting basal transcription. These results, taken together with previous studies of Sp1 and dTAFII110, establish that different activators interact with distinct TAFs in the TFIID complex and that TAFs can contact both activators and basal factors.
病毒反式激活因子VP16增强RNA聚合酶II转录需要TFIID复合物，该复合物由TATA结合蛋白（TBP）和TBP相关因子（TAFs）组成。在此，我们报道了果蝇TFIID的一个亚基——果蝇TAFII40（dTAFII40）的分子克隆、表达及生化特性。体外蛋白质-蛋白质相互作用分析显示dTAFII40与一个39个氨基酸的VP16激活结构域之间存在直接结合。此外，亲和层析表明基础因子TFIIB与固定化的dTAFII40直接结合。由于VP16也结合TFIIB，我们的结果提示激活因子、辅激活因子和基础转录因子之间存在三元相互作用。针对dTAFII40的抗体抑制了GAL4-VP16的激活作用，而不影响基础转录。这些结果与之前对Sp1和dTAFII110的研究一起表明，不同的激活因子与TFIID复合物中不同的TAFs相互作用，并且TAFs可以同时接触激活因子和基础因子。
