PDF(Pubmed)
Abstract：
RNA polymerase III (Pol III) is responsible for transcribing 5S ribosomal RNA (5S rRNA), tRNAs, and other short non-coding RNAs. Its recruitment to the 5S rRNA promoter requires transcription factors TFIIIA, TFIIIC, and TFIIIB. Here, we use cryoelectron microscopy (cryo-EM) to visualize the S. cerevisiae complex of TFIIIA and TFIIIC bound to the promoter. Gene-specific factor TFIIIA interacts with DNA and acts as an adaptor for TFIIIC-promoter interactions. We also visualize DNA binding of TFIIIB subunits, Brf1 and TBP (TATA-box binding protein), which results in the full-length 5S rRNA gene wrapping around the complex. Our smFRET study reveals that the DNA within the complex undergoes both sharp bending and partial dissociation on a slow timescale, consistent with the model predicted from our cryo-EM results. Our findings provide new insights into the transcription initiation complex assembly on the 5S rRNA promoter and allow us to directly compare Pol III and Pol II transcription adaptations.
摘要：
RNA聚合酶III（PolIII）负责转录5S核糖体RNA（5SrRNA），tRNAs,和其他短的非编码RNA。它募集到5SrRNA启动子需要转录因子TFIIIA，TFIIC,和TFIIIB。这里,我们使用低温电子显微镜（cryo-EM）观察与启动子结合的TFIIIA和TFIIIC的酿酒酵母复合物。基因特异性因子TFIIIA与DNA相互作用并充当TFIIIC-启动子相互作用的衔接子。我们还可视化TFIIIB亚基的DNA结合，Brf1和TBP（TATA盒结合蛋白），这导致全长5SrRNA基因包裹在复合物周围。我们的smFRET研究表明，复合物中的DNA在缓慢的时间尺度上经历了急剧的弯曲和部分解离，与我们的低温EM结果预测的模型一致。我们的发现为5SrRNA启动子上的转录起始复合物组装提供了新的见解，并使我们能够直接比较PolIII和PolII转录适应。
