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Architecture of the multi‐functional SAGA complex and the molecular mechanism of holding TBP
The FEBS Journal ( IF 5.4 ) Pub Date : 2020-09-18 , DOI: 10.1111/febs.15563
Adam Ben-Shem 1, 2, 3 , Gabor Papai 1, 2, 3 , Patrick Schultz 1, 2, 3
Affiliation  

In eukaryotes, transcription of protein encoding genes is initiated by the controlled deposition of the TATA‐box binding protein TBP onto gene promoters, followed by the ordered assembly of a pre‐initiation complex. The SAGA co‐activator is a 19‐subunit complex that stimulates transcription by the action of two chromatin‐modifying enzymatic modules, a transcription activator binding module, and by delivering TBP. Recent cryo electron microscopy structures of yeast SAGA with bound nucleosome or TBP reveal the architecture of the different functional domains of the co‐activator. An octamer of histone fold domains is found at the core of SAGA. This octamer, which deviates considerably from the symmetrical analogue forming the nucleosome, establishes a peripheral site for TBP binding where steric hindrance represses interaction with spurious DNA. The structures point to a mechanism for TBP delivery and release from SAGA that requires TFIIA and whose efficiency correlates with the affinity of DNA to TBP. These results provide a structural basis for understanding specific TBP delivery onto gene promoters and the role played by SAGA in regulating gene expression. The properties of the TBP delivery machine harboured by SAGA are compared with the TBP loading device present in the TFIID complex and show multiple similitudes.

中文翻译:

多功能SAGA配合物的结构和持有TBP的分子机理

在真核生物中,通过将TATA盒结合蛋白TBP受控沉积到基因启动子上,然后有序组装预启动复合体,来启动蛋白质编码基因的转录。SAGA辅助激活剂是一种19亚基复合物,可通过两个染色质修饰酶模块,一个转录激活剂结合模块以及通过传递TBP的作用来刺激转录。酵母SAGA与结合的核小体或TBP的最新低温电子显微镜结构揭示了共激活子不同功能域的结构。组蛋白折叠域的八聚体位于SAGA的核心。该八聚体大大偏离了形成核小体的对称类似物,为TBP结合建立了一个外围位点,在该位点,空间位阻抑制了与假DNA的相互作用。该结构指向TBP传递和从SAGA释放的机制,这需要TFIAA,并且其效率与DNA对TBP的亲和力相关。这些结果提供了结构上的基础,以了解特定的TBP传递到基因启动子上,以及SAGA在调节基因表达中的作用。将SAGA拥有的TBP输送机的性能与TFIID复合体中存在的TBP加载设备进行比较,并显示出多种相似性。
更新日期:2020-09-18
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