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Updated: Nov 6, 2025

Isolation of Labile Multi-protein Complexes by in vivo Controlled Cellular Cross-Linking and Immuno-magnetic Affinity Chromatography
Published on: March 9, 2010
Structures of the human Mediator and Mediator-bound preinitiation complex
Xizi Chen1, Xiaotong Yin1, Jiabei Li1
1Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Radiation Oncology, and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China.
Transcription factor IID (TFIID) orchestrates preinitiation complex assembly. The study reveals how TFIID-Mediator interactions stabilize RNA polymerase II C-terminal domain for phosphorylation, crucial for transcription initiation.
Area of Science:
- Molecular Biology
- Structural Biology
- Gene Regulation
Background:
- Transcription factor IID (TFIID) is essential for RNA polymerase II (Pol II) transcription initiation.
- The Mediator complex stimulates transcription and regulates Pol II C-terminal domain (CTD) phosphorylation by CDK7.
Purpose of the Study:
- To determine the structures of human Mediator and TFIID-based PIC-Mediator complexes.
- To elucidate the structural mechanisms of Mediator reorganization and CTD phosphorylation during transcription initiation.
Main Methods:
- Near-atomic resolution cryo-electron microscopy
- Structural determination of Mediator and TFIID-Mediator complexes in distinct conformations
Main Results:
- PIC-Mediator assembly induces Mediator reorganization, forming a Head-Middle sandwich.
- This structure stabilizes CTD segments and facilitates CDK7-mediated phosphorylation via a CTD-gating mechanism.
- TFIID architecture modulates Mediator organization and TFIIH stabilization.
Conclusions:
- TFIID plays a critical role in orchestrating PIC-Mediator assembly.
- A CTD-gating mechanism involving Mediator reorganization is proposed for efficient CTD phosphorylation.
- These findings provide insights into the regulation of transcription initiation.
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