Mechanisms of transcriptional initiation and regulation mediated by general transcription factor TFIID

在真核生物中，蛋白质编码基因由RNA聚合酶II（pol II）与一般转录因子（GTF）一起转录。TFIID是由TATA元件结合蛋白（TBP）和14个TBP相关因子（TAF）组成的最大的GTF，在TATA缺失启动子的转录中起着关键作用。在后生动物中，除了TATA元件之外的几个核心启动子元件被认为是TFIID的识别位点。然而，目前还不清楚是否功能同源元件也存在于酿酒酵母中的TATA-少启动子。在这里，我们确定的顺式元件，以支持正常水平的转录和准确的启动内的TATA和TFIID依赖性RPS 5核心启动子的网站。系统的突变分析表明，这些活动所需的多个AT丰富的序列，并出现TFIID的识别位点的功能。这些序列的单个拷贝可以支持从内源启动子的准确起始，表明它们携带高度冗余的功能。这些结果显示了酵母TATA-少启动子的新结构，并支持pol II从募集位点扫描DNA下游，同时寻找合适的起始位点的模型。

In eukaryotes, protein-coding genes are transcribed by RNA polymerase II (pol II) together with general transcription factors (GTFs). TFIID, the largest GTF composed of TATA element-binding protein (TBP) and 14 TBP-associated factors (TAFs), plays a critical role in transcription from TATA-less promoters. In metazoans, several core promoter elements other than the TATA element are thought to be recognition sites for TFIID. However, it is unclear whether functionally homologous elements also exist in TATA-less promoters in Saccharomyces cerevisiae. Here, we identify the cis-elements required to support normal levels of transcription and accurate initiation from sites within the TATA-less and TFIID-dependent RPS5 core promoter. Systematic mutational analyses show that multiple AT-rich sequences are required for these activities and appear to function as recognition sites for TFIID. A single copy of these sequences can support accurate initiation from the endogenous promoter, indicating that they carry highly redundant functions. These results show a novel architecture of yeast TATA-less promoters and support a model in which pol II scans DNA downstream from a recruited site, while searching for appropriate initiation site(s).