Molecular structures of unbound and transcribing RNA polymerase III.
Molecular structures of unbound and transcribing RNA polymerase III.
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DOI：
10.1038/nature16143
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发表时间：
2015-12-10
期刊：
影响因子：
64.8
通讯作者：
Müller CW
中科院分区：
文献类型：
--
作者：
Hoffmann NA;Jakobi AJ;Moreno-Morcillo M;Glatt S;Kosinski J;Hagen WJ;Sachse C;Müller CW
编码小结构RNA如tRNA、剪接体U6 snRNA和核糖体5S RNA的基因的转录由RNA聚合酶III（Pol III）进行，RNA聚合酶III是最大但结构特征最少的真核RNA聚合酶。用冷冻电镜观察了S.酿酒酵母Pol III延伸复合物在3.9 nm分辨率和两种不同构象的载脂蛋白Pol III酶分别在4.6和4.7 nm分辨率，允许首次建立Pol III的17-亚基原子模型。重建揭示了C82/C34/C31异源三聚体在接近茎的精确取向。C53/C37异二聚体将参与转录终止的残基定位在靠近非模板DNA链的位置。在载脂蛋白Pol III结构中，柄采用不同的取向，并与夹的闭合和开放构象相结合。我们的研究结果提供了新的见解Pol III特异性转录和Pol III对其小的转录靶点的适应。
Transcription of genes encoding small structured RNAs such as tRNAs, spliceosomal U6 snRNA and ribosomal 5S RNA is carried out by RNA polymerase III (Pol III), the largest yet structurally least characterized eukaryotic RNA polymerase. The cryo-EM structures of the S. cerevisiae Pol III elongating complex at 3.9 Å resolution and the apo Pol III enzyme in two different conformations at 4.6 and 4.7 Å resolution, respectively, allow for the first time to build a 17-subunit atomic model of Pol III. The reconstructions reveal the precise orientation of the C82/C34/C31 heterotrimer in close proximity to the stalk. The C53/C37 heterodimer positions residues involved in transcription termination close to the non-template DNA strand. In the apo Pol III structures, the stalk adopts different orientations coupled with closed and open conformations of the clamp. Our results provide novel insights into Pol III-specific transcription and the adaptation of Pol III towards its small transcriptional targets.