Martinez E, Chiang C M, Ge H, Roeder R G
Laboratory of Biochemistry and Molecular Biology, Rockefeller University, New York, NY 10021.
EMBO J. 1994 Jul 1;13(13):3115-26. doi: 10.1002/j.1460-2075.1994.tb06610.x.
The RNA polymerase II (Pol II) basal transcription factor TFIID is composed of the TATA box-binding protein (TBP) and several TBP-associated factors (TAFs). TBP is required for Pol II transcription from TATA-containing and TATA-less promoters. TATA-less promoters of mRNA-encoding genes often contain an initiator element at the transcription start site that is sufficient to direct accurate Pol II transcription. Here we address the mechanisms of functional TBP recruitment to the TATA-less initiator-dependent promoter of the mouse terminal deoxynucleotidyl transferase (TdT) gene. We show that the natural TATA-less TdT initiator region is sufficient to promote low levels of specific transcription in vitro and to direct the assembly of a stable preinitiation complex. In contrast to what is observed for several other promoters lacking a consensus TATA element, the TATA-binding activity of TBP is not required for the functional recruitment of TFIID to the natural TATA-less TdT and beta-polymerase promoters. Moreover, a comparison of TBP and highly purified epitope-tagged TFIID reveals that one or several TAFs function independently of distal regulatory elements to mediate initiator-directed (basal) transcription from the natural TATA-less TdT core promoter in crude nuclear extracts. Furthermore, by using a transcription system reconstituted with purified components, we present the first evidence for a basal transcription function of TAFs through the TdT initiator element. Altogether, our results suggest an alternative pathway for TFIID recruitment to initiator-dependent TATA-less class II promoters in which TAF(s) recruit TBP by interacting either directly or indirectly with the initiator region.
RNA聚合酶II（Pol II）基础转录因子TFIID由TATA框结合蛋白（TBP）和几个TBP相关因子（TAFs）组成。TBP是含TATA和不含TATA启动子的Pol II转录所必需的。编码mRNA的基因的无TATA启动子通常在转录起始位点含有一个起始子元件，该元件足以指导准确的Pol II转录。在这里，我们探讨功能性TBP募集到小鼠末端脱氧核苷酸转移酶（TdT）基因的无TATA起始子依赖性启动子的机制。我们表明，天然的无TATA的TdT起始子区域足以在体外促进低水平的特异性转录，并指导稳定的起始前复合物的组装。与缺乏共有TATA元件的其他几个启动子所观察到的情况相反，TBP的TATA结合活性对于TFIID功能性募集到天然的无TATA的TdT和β-聚合酶启动子不是必需的。此外，对TBP和高度纯化的表位标记的TFIID的比较表明，一个或几个TAFs独立于远端调节元件发挥作用，以介导粗核提取物中天然无TATA的TdT核心启动子的起始子指导的（基础）转录。此外，通过使用用纯化成分重建的转录系统，我们首次证明了TAFs通过TdT起始子元件具有基础转录功能。总之，我们的结果表明了TFIID募集到依赖起始子的无TATA II类启动子的另一种途径，其中TAF通过直接或间接与起始子区域相互作用来募集TBP。
