Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
EMBL Imaging Centre, European Molecular Biology Laboratory, Heidelberg, Germany.
Sci Adv. 2022 Apr 22;8(16):eabn5725. doi: 10.1126/sciadv.abn5725. Epub 2022 Apr 20.
Preribosomal RNA is selectively transcribed by RNA polymerase (Pol) I in eukaryotes. The yeast transcription factor upstream activating factor (UAF) represses Pol II transcription and mediates Pol I preinitiation complex (PIC) formation at the 35 ribosomal RNA gene. To visualize the molecular intermediates toward PIC formation, we determined the structure of UAF in complex with native promoter DNA and transcription factor TATA-box-binding protein (TBP). We found that UAF recognizes DNA using a hexameric histone-like scaffold with markedly different interactions compared with the nucleosome and the histone-fold-rich transcription factor IID (TFIID). In parallel, UAF positions TBP for Core Factor binding, which leads to Pol I recruitment, while sequestering it from DNA and Pol II/III-specific transcription factors. Our work thus reveals the structural basis of RNA Pol selection by a transcription factor.
原核生物核糖体 RNA 是由 RNA 聚合酶（Pol）I 选择性转录的。酵母转录因子上游激活因子（UAF）抑制 Pol II 转录，并在 35 核糖体 RNA 基因处介导 Pol I 起始前复合物（PIC）的形成。为了可视化形成 PIC 的分子中间产物，我们确定了 UAF 与天然启动子 DNA 和转录因子 TATA 框结合蛋白（TBP）的复合物结构。我们发现，UAF 使用具有明显不同于核小体和富含组蛋白折叠的转录因子IID（TFIID）的六聚体组蛋白样支架识别 DNA。同时，UAF 为核心因子结合定位 TBP，这导致 Pol I 的募集，同时将其与 DNA 和 Pol II/III 特异性转录因子隔离开来。因此，我们的工作揭示了转录因子选择 RNA Pol 的结构基础。
