クロマチンによるcGASの結合と自己抑制の構造的基礎

Sebastian Michalski^1,2, Carina C de Oliveira Mann^1,2, Che A Stafford^1,2

¹Gene Center, Ludwig-Maximilians-Universität, Munich, Germany.

Nature

|September 10, 2020

まとめ

クロマチンは核内のサイクルGMP- AMP合成酵素 (cGAS) を隔離し抑制する. ヒストンと酸性パッチが関与するこの相互作用は,cGASがDNAと結合し,自己免疫反応を誘発するのを防ぐ.

科学分野:

免疫学
分子生物学
構造生物学

背景:

サイクルGMP-AMP合成酵素 (cGAS) は,細胞塩基DNAを検出する重要な先天性免疫センサーである.
cGASの活性化により,STING媒介の免疫反応が起こりますが,自己DNAを標的にし,自己免疫に寄与します.
最近の研究では,cGASが核に局所化し,自己DNA認識を防ぐメカニズムが必要であることが示されています.

研究の目的:

核のcGASがクロマチンによって隔離され,抑制されるメカニズムを解明する.
クロマチンの結合が,核の自己DNAに対するcGASの自己反応を防ぐ方法を理解する.

主な方法:

クリオ電子顕微鏡で,核細胞に結合したcGASの構造を決定する.
DNAと核細胞がcGASに結合することを評価する生化学的測定法.

主要な成果:

クリオ-EM構造は,DNAではなく,核子の酸性パッチでヒストン2A-2BにcGAS結合を明らかにする.
この相互作用は,cGASのDNA結合部位Bを埋めて,ダイマー形成と活性を抑制する.
核粒子の酸性パッチは,活性ゲノム領域の近くでも,cGAS結合でDNAを効果的に上回ります.

結論:

核のcGASは,核体ヒストンと酸性パッチとの相互作用によって,クロマチンによって積極的に隔離され,抑制されます.
このクロマチンの媒介による阻害は,核の自己DNAへの自己反応を防ぐために重要なメカニズムとして機能する.
この相互作用を理解することで免疫調節と自己免疫疾患の洞察が得られます

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