European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117, Heidelberg, Germany.
Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, 69120, Heidelberg, Germany.
Nat Commun. 2020 Sep 30;11(1):4905. doi: 10.1038/s41467-020-18707-y.
Transcription factor (TF) IIIC is a conserved eukaryotic six-subunit protein complex with dual function. It serves as a general TF for most RNA polymerase (Pol) III genes by recruiting TFIIIB, but it is also involved in chromatin organization and regulation of Pol II genes through interaction with CTCF and condensin II. Here, we report the structure of the S. cerevisiae TFIIIC subcomplex τA, which contains the most conserved subunits of TFIIIC and is responsible for recruitment of TFIIIB and transcription start site (TSS) selection at Pol III genes. We show that τA binding to its promoter is auto-inhibited by a disordered acidic tail of subunit τ95. We further provide a negative-stain reconstruction of τA bound to the TFIIIB subunits Brf1 and TBP. This shows that a ruler element in τA achieves positioning of TFIIIB upstream of the TSS, and suggests remodeling of the complex during assembly of TFIIIB by TFIIIC.
转录因子 (TF) IIIC 是一种保守的真核六亚基蛋白复合物，具有双重功能。它通过募集 TFIIIB 作为大多数 RNA 聚合酶 (Pol) III 基因的通用 TF，但它也通过与 CTCF 和凝聚素 II 的相互作用参与染色质组织和 Pol II 基因的调控。在这里，我们报告了酿酒酵母 TFIIIC 亚基 τA 的结构，该结构包含 TFIIIC 最保守的亚基，负责募集 TFIIIB 和 Pol III 基因转录起始位点 (TSS) 的选择。我们表明，τA 与其启动子的结合受到亚基 τ95 的无规酸性尾巴的自动抑制。我们进一步提供了 τA 与 TFIIIB 亚基 Brf1 和 TBP 结合的负染重建。这表明 τA 中的标尺元件实现了 TFIIIB 在 TSS 上游的定位，并表明在 TFIIIC 组装 TFIIIB 期间复合物的重塑。
