Gene Center and Department of Biochemistry, Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
Nature. 2013 Oct 31;502(7473):650-5. doi: 10.1038/nature12712. Epub 2013 Oct 23.
Transcription of ribosomal RNA by RNA polymerase (Pol) I initiates ribosome biogenesis and regulates eukaryotic cell growth. The crystal structure of Pol I from the yeast Saccharomyces cerevisiae at 2.8 Å resolution reveals all 14 subunits of the 590-kilodalton enzyme, and shows differences to Pol II. An 'expander' element occupies the DNA template site and stabilizes an expanded active centre cleft with an unwound bridge helix. A 'connector' element invades the cleft of an adjacent polymerase and stabilizes an inactive polymerase dimer. The connector and expander must detach during Pol I activation to enable transcription initiation and cleft contraction by convergent movement of the polymerase 'core' and 'shelf' modules. Conversion between an inactive expanded and an active contracted polymerase state may generally underlie transcription. Regulatory factors can modulate the core-shelf interface that includes a 'composite' active site for RNA chain initiation, elongation, proofreading and termination.
核糖体 RNA 的转录由 RNA 聚合酶（Pol）I 启动，从而启动核糖体生物发生并调节真核细胞生长。来自酿酒酵母 Saccharomyces cerevisiae 的 Pol I 的 2.8 Å 分辨率晶体结构揭示了 590 千道尔顿酶的所有 14 个亚基，并显示出与 Pol II 的差异。一个“扩展”元件占据 DNA 模板位点，并稳定具有展开的桥螺旋的扩展活性中心裂缝。一个“连接”元件侵入相邻聚合酶的裂缝，并稳定无活性的聚合酶二聚体。在 Pol I 激活过程中，连接器和扩展器必须分离，以便通过聚合酶“核心”和“支架”模块的会聚运动进行转录起始和裂缝收缩。从无活性扩展到活性收缩聚合酶状态的转换可能是转录的基础。调节因子可以调节包括 RNA 链起始、延伸、校对和终止的“复合”活性位点的核心-支架界面。
