One class of transcriptional activation domains stimulates the concerted binding of TFIIA and TFIID to promoter DNA. To test whether this DA-complex assembly activity contributes significantly to the overall mechanism of activation in vivo, we analyzed mutants of the 38-amino-acid residue VP16C activation subdomain from herpes simplex virus. An excellent correlation was observed between the in vivo activation function of these mutants and their in vitro DA-complex assembly activity. Mutants severely defective for in vivo activation also showed reduced in vitro binding to native TFIIA. No significant correlation between in vivo activation function and in vitro binding to human TATA binding protein, human TFIIB, or Drosophila melanogaster TAFII40 was observed for this set of VP16C mutants. These results argue that the ability of VP16C to increase the rate and extent of DA-complex assembly makes a significant contribution to the overall mechanism of transcriptional activation in vivo.
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机译：一类转录激活结构域刺激TFIIA和TFIID与启动子DNA的协同结合。为了测试这种DA复合物组装活性是否对体内激活的总体机制有显着贡献，我们分析了单纯疱疹病毒的38个氨基酸残基VP16C激活亚结构域的突变体。在这些突变体的体内激活功能与其体外DA-复合物组装活性之间观察到极好的相关性。体内激活严重缺陷的突变体还显示出与天然TFIIA的体外结合减少。对于这组VP16C突变体，在体内激活功能与体外与人TATA结合蛋白，人TFIIB或果蝇 TAF II 40的结合之间没有显着相关性。这些结果表明，VP16C增加DA复合物装配的速率和程度的能力对体内转录激活的整体机制做出了重大贡献。
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