马疱疹病毒1（EHV-1）的立即早期蛋白（IEP）与α疱疹病毒的IEP具有广泛的同源性，并具有反式激活所必需的结构域，包括酸性反式激活域（TAD）和DNA结合域，TFIIB,还有TBP.我们的数据表明，IEP直接与转录因子TFIIA相互作用，已知其稳定TBP和TFIID与核心启动子的TATA盒的结合。当EICP0启动子的TATA盒突变为无功能的TATA盒时，IEP介导的反式激活从22倍降低到7倍。IEP以TATA基序依赖性方式反式激活病毒启动子。我们先前的数据表明，当IEP结合序列（IEBS）位于TATA框的26bp内时，IEP能够抑制其自身的启动子。当IEBS位于TATA框上游100bp时，IEP介导的反式激活与缺少IEBS的最小IE（nt-89至73）启动子非常相似。随着从IEBS到TATA框的距离减小，IEP介导的反式激活逐渐减少，表明位于TATA盒序列100bp内的IEBS充当距离依赖性抑制元件。这些结果表明，IEP介导的全反式激活需要核心启动子的共有TATA盒，但不是它与同源序列(IEBS)的结合。
The immediate-early protein (IEP) of equine herpesvirus 1 (EHV-1) has extensive homology to the IEP of alphaherpesviruses and possesses domains essential for trans-activation, including an acidic trans-activation domain (TAD) and binding domains for DNA, TFIIB, and TBP. Our data showed that the IEP directly interacted with transcription factor TFIIA, which is known to stabilize the binding of TBP and TFIID to the TATA box of core promoters. When the TATA box of the EICP0 promoter was mutated to a nonfunctional TATA box, IEP-mediated trans-activation was reduced from 22-fold to 7-fold. The IEP trans-activated the viral promoters in a TATA motif-dependent manner. Our previous data showed that the IEP is able to repress its own promoter when the IEP-binding sequence (IEBS) is located within 26-bp from the TATA box. When the IEBS was located at 100 bp upstream of the TATA box, IEP-mediated trans-activation was very similar to that of the minimal IE(nt -89 to +73) promoter lacking the IEBS. As the distance from the IEBS to the TATA box decreased, IEP-mediated trans-activation progressively decreased, indicating that the IEBS located within 100 bp from the TATA box sequence functions as a distance-dependent repressive element. These results indicated that IEP-mediated full trans-activation requires a
consensus TATA box of core promoters, but not its binding to the cognate sequence (IEBS).
