Emami K H, Jain A, Smale S T
Howard Hughes Medical Institute, Molecular Biology Institute, University of California, Los Angeles, School of Medicine, Los Angeles, California 90095-1662, USA.
Genes Dev. 1997 Nov 15;11(22):3007-19. doi: 10.1101/gad.11.22.3007.
The TFIID complex interacts with at least three types of core promoter elements within protein-coding genes, including TATA, initiator (Inr), and downstream promoter elements. We have begun to explore the mechanism by which the TFIID-Inr interaction leads to functional synergy between TATA and Inr elements during both basal and activated transcription. In DNase I footprinting assays, GAL4-VP16 recruited TFIID-TFIIA to core promoters containing either a TATA box, an Inr, or both TATA and Inr elements, with synergistic interactions apparent on the TATA-Inr promoter. Appropriate spacing between the two elements was essential for the synergistic binding. Despite the sequence-specific TFIID-Inr interactions, gel shift experiments revealed that TFIID alone possesses similar affinities for the TATA-Inr and TATA promoters. Interestingly, however, recombinant TFIIA strongly and selectively enhanced TFIID binding to the TATA-Inr promoter, with little effect on binding to the TATA promoter. Studies of the natural adenovirus major late promoter confirmed these findings, despite the existence of specific but nonfunctional TFIID interactions downstream of the Inr in that promoter. These results suggest that a TFIIA-induced conformational change is essential for the sequence-specific TFIID-Inr interaction to occur with sufficient affinity to support the functional synergism between TATA and Inr elements.
TFIID复合物与蛋白质编码基因内至少三种类型的核心启动子元件相互作用，包括TATA、起始子（Inr）和下游启动子元件。我们已经开始探索在基础转录和激活转录过程中，TFIID-Inr相互作用导致TATA和Inr元件之间功能协同的机制。在DNA酶I足迹分析中，GAL4-VP16将TFIID-TFIIA招募到含有TATA框、Inr或同时含有TATA和Inr元件的核心启动子上，在TATA-Inr启动子上明显存在协同相互作用。两个元件之间的适当间距对于协同结合至关重要。尽管存在序列特异性的TFIID-Inr相互作用，但凝胶迁移实验表明，单独的TFIID对TATA-Inr启动子和TATA启动子具有相似的亲和力。然而，有趣的是，重组TFIIA强烈且选择性地增强了TFIID与TATA-Inr启动子的结合，而对与TATA启动子的结合影响很小。对天然腺病毒主要晚期启动子的研究证实了这些发现，尽管在该启动子的Inr下游存在特异性但无功能的TFIID相互作用。这些结果表明，TFIIA诱导的构象变化对于序列特异性的TFIID-Inr相互作用以足够的亲和力发生以支持TATA和Inr元件之间的功能协同至关重要。
