哺乳類のRNAポリメラーゼII前始動複合体の構造

Shintaro Aibara¹, Sandra Schilbach¹, Patrick Cramer²

¹Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.

Nature

|April 26, 2021

まとめ

研究者は,細胞発達の過程で遺伝子調節のためのプロモーターを開くために,転写因子TFIIHがDNAをどのように歪めるかを明らかにする,前始動複合体 (PIC) 構造を視覚化しました.

科学分野:

分子生物学
遺伝学
生物化学

背景:

転写の開始は,哺乳類の細胞における遺伝子の活性を調節するために極めて重要です.
RNAポリメラーゼII (Pol II) と一般的な転写因子を含むプレイニシエーション複合体 (PIC) は,開いたプロモーターDNAに組み合わされる.
以前の研究では,酵母とヒトのPICの構造と,TFIIHによるDNA開封のモデルが確立されました.

研究の目的:

閉ざされたおよび開かれたプロモーターDNAによるヒトPICの高解像度構造を決定する.
TFIIHトランスロカゼXPBによるDNA開閉のメカニズムを解明する.

主な方法:

高解像度冷凍電子顕微鏡 (cryo-EM) を使用して,PIC構造を可視化しました.
閉ざされたおよび開かれたプロモーターDNAのPICの構造は2.5~2. 8 Åの解像度で決定された.
TFIIHの構造は2.9~4.0 Åの解像度で解析され,XPBは異なる転位状態で捉えられた.

主要な成果:

Sus scrofa domesticus Pol IIを用いたヒトPICの冷凍-EM構造を決定した.
TFIIHのXPBトランスロケーションは,トランスロケーション前と後の状態で観察され,DNAの歪みを誘導しました.
TATAボックスの下流で約30塩基対の2段階のDNA開きが示され,TFIIHの分離につながった.

結論:

TFIIHのXPBは,DNAの歪みを通してDNAの開きを開始する上で重要な役割を果たします.
2段階のDNA開きメカニズムと,その後のTFIIH分離は,RNA鎖の開始を調節する可能性があります.

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