Department of Chemistry, Georgia State University, Atlanta, GA, USA.
Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA.
Nat Commun. 2023 May 13;14(1):2758. doi: 10.1038/s41467-023-38416-6.
Transcription factor IIH (TFIIH) is a protein assembly essential for transcription initiation and nucleotide excision repair (NER). Yet, understanding of the conformational switching underpinning these diverse TFIIH functions remains fragmentary. TFIIH mechanisms critically depend on two translocase subunits, XPB and XPD. To unravel their functions and regulation, we build cryo-EM based TFIIH models in transcription- and NER-competent states. Using simulations and graph-theoretical analysis methods, we reveal TFIIH's global motions, define TFIIH partitioning into dynamic communities and show how TFIIH reshapes itself and self-regulates depending on functional context. Our study uncovers an internal regulatory mechanism that switches XPB and XPD activities making them mutually exclusive between NER and transcription initiation. By sequentially coordinating the XPB and XPD DNA-unwinding activities, the switch ensures precise DNA incision in NER. Mapping TFIIH disease mutations onto network models reveals clustering into distinct mechanistic classes, affecting translocase functions, protein interactions and interface dynamics.
转录因子 IIH（TFIIH）是转录起始和核苷酸切除修复（NER）所必需的蛋白质组装体。然而，对于这些不同 TFIIH 功能的构象转换的理解仍然是零散的。TFIIH 机制严重依赖于两个转位酶亚基，XPB 和 XPD。为了揭示它们的功能和调节机制，我们构建了在转录和 NER 功能状态下基于 cryo-EM 的 TFIIH 模型。使用模拟和图论分析方法，我们揭示了 TFIIH 的全局运动，将 TFIIH 划分为动态社区，并展示了 TFIIH 如何根据功能上下文重塑自身和自我调节。我们的研究揭示了一种内部调节机制，该机制可切换 XPB 和 XPD 的活性，使它们在 NER 和转录起始之间相互排斥。通过顺序协调 XPB 和 XPD 的 DNA 解旋活性，该开关可确保在 NER 中进行精确的 DNA 切割。将 TFIIH 疾病突变映射到网络模型上揭示了聚类成不同的机制类别，影响转位酶功能、蛋白质相互作用和界面动力学。
