Chiannilkulchai N, Stalder R, Riva M, Carles C, Werner M, Sentenac A
Service de Biochimie et Génétique Moléculaire, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
Mol Cell Biol. 1992 Oct;12(10):4433-40. doi: 10.1128/mcb.12.10.4433-4440.1992.
RNA polymerase C (III) promotes the transcription of tRNA and 5S RNA genes. In Saccharomyces cerevisiae, the enzyme is composed of 15 subunits, ranging from 160 to about 10 kDa. Here we report the cloning of the gene encoding the 82-kDa subunit, RPC82. It maps as a single-copy gene on chromosome XVI. The UCR2 gene was found in the opposite orientation only 340 bp upstream of the RPC82 start codon, and the end of the SKI3 coding sequence was found only 117 bp downstream of the RPC82 stop codon. The RPC82 gene encodes a protein with a predicted M(r) of 73,984, having no strong sequence similarity to other known proteins. Disruption of the RPC82 gene was lethal. An rpc82 temperature-sensitive mutant, constructed by in vitro mutagenesis of the gene, showed a deficient rate of tRNA relative to rRNA synthesis. Of eight RNA polymerase C genes tested, only the RPC31 gene on a multicopy plasmid was capable of suppressing the rpc82(Ts) defect, suggesting an interaction between the polymerase C 82-kDa and 31-kDa subunits. A group of RNA polymerase C-specific subunits are proposed to form a substructure of the enzyme.
RNA聚合酶C（III）促进tRNA和5S RNA基因的转录。在酿酒酵母中，该酶由15个亚基组成，分子量从160 kDa到约10 kDa不等。在此，我们报道了编码82-kDa亚基RPC82的基因的克隆。它定位于第十六号染色体上的单拷贝基因。发现UCR2基因以相反的方向位于RPC82起始密码子上游仅340 bp处，并且SKI3编码序列的末端仅位于RPC82终止密码子下游117 bp处。RPC82基因编码一种预测分子量为73,984的蛋白质，与其他已知蛋白质没有很强的序列相似性。RPC82基因的破坏是致死性的。通过对该基因进行体外诱变构建的rpc82温度敏感突变体，相对于rRNA合成，其tRNA合成速率不足。在测试的八个RNA聚合酶C基因中，只有多拷贝质粒上的RPC31基因能够抑制rpc82（Ts）缺陷，这表明聚合酶C的82-kDa和31-kDa亚基之间存在相互作用。有人提出一组RNA聚合酶C特异性亚基形成该酶的一个亚结构。
