RNA polymerase I remains intact without subunit exchange through multiple rounds of transcription in Saccharomyces cerevisiae
RNA polymerase I remains intact without subunit exchange through multiple rounds of transcription in Saccharomyces cerevisiae
复制标题
DOI：
10.1073/pnas.0406746101
复制
发表时间：
2004-10-19
影响因子：
11.1
通讯作者：
Nomura, M
中科院分区：
文献类型：
--
作者：
Schneider, DA;Nomura, M
之前使用哺乳动物细胞进行的实验表明，每轮转录后，RNA 聚合酶 I (Pol I) 都会解离成亚基，这些亚基作为单独的亚基离开和重新进入核仁，然后形成新的起始复合物。在这项研究中，我们表明，当 Pol I 不参与 rRNA 转录时，Pol I 的大小和亚基组成没有显着变化，这是由于缺乏 Pol I 特异性 rDNA 模板或需要 Rrn3p 的转录起始步骤的特异性抑制造成的。事实上，在设计用于测定活性 Pol 1-Rrn3p 复合物的体外转录系统中，从完全缺乏 rDNA 重复的细胞中纯化的 Pol I 比从野生型细胞中纯化的 Pol I 更具活性。此外，对预先存在的 Pol I 和新合成的 Pol I 之间 A135 和 A190 亚基交换的测量表明，Pol I 的这两个最大的亚基不会通过体内多轮转录而解离。因此，Pol I 不是动态蛋白质复合物，而是稳定的酶。
Previous experiments using mammalian cells suggested that after each round of transcription, RNA polymerase I (Pol I) dissociates into subunits that leave and reenter the nucleolus as individual subunits, before formation of a new initiation complex. In this study, we show that the size and subunit composition of Pol I did not change significantly when Pol I was not engaged in rRNA transcription, brought about by either the absence of Pol I-specific rDNA template or specific inhibition of the transcription initiation step that requires Rrn3p. In fact, Pol I purified from cells completely lacking rDNA repeats was more active than when purified from wild-type cells in an in vitro transcription system designed to assay active Pol 1-Rrn3p complexes. Furthermore, measurements of the exchange of A135 and A190 subunits between preexistent Pol I and newly synthesized Pol I showed that these two largest subunits of Pol I do not disassociate through many rounds of transcription in vivo. Thus, Pol I is not a dynamic protein complex but rather a stable enzyme.