Yao Y, Yamamoto K, Nishi Y, Nogi Y, Muramatsu M
Department of Biochemistry, Saitama Medical School, 38 Morohongo, Moroyama, Iruma-gun, Saitama 350-04, Japan.
J Biol Chem. 1996 Dec 20;271(51):32881-5. doi: 10.1074/jbc.271.51.32881.
We have previously isolated a mouse RPA40 (mRPA40) cDNA encoding the 40-kDa subunit of mouse RNA polymerase I and demonstrated that mRPA40 is a mouse homolog of the yeast subunit AC40, which is a subunit of RNA polymerases I and III, having a limited homology to bacterial RNA polymerase subunit alpha (Song, C. Z., Hanada, K., Yano, K., Maeda, Y., Yamamoto, K., and Muramatsu, M. (1994) J. Biol. Chem. 269, 26976-26981). In an extension of the study we have now cloned mouse RPA16 (mRPA16) cDNA encoding the 16-kDa subunit of mouse RNA polymerase I by a yeast two-hybrid system using mRPA40 as a bait. The deduced amino acid sequence shows 45% identity to the yeast subunit AC19 of RNA polymerases I and III, known to associate with AC40, and a local similarity to bacterial alpha subunit. We have shown that mRPA40 mutants failed to interact with mRPA16 and that neither mRPA16 nor mRPA40 can interact by itself in the yeast two-hybrid system. These results suggest that higher eukaryotic RNA polymerase I conserves two distinct alpha-related subunits that function to associate with each other in an early stage of RNA polymerase I assembly.
我们之前分离出了编码小鼠RNA聚合酶I 40 kDa亚基的小鼠RPA40（mRPA40）cDNA，并证明mRPA40是酵母亚基AC40的小鼠同源物，AC40是RNA聚合酶I和III的一个亚基，与细菌RNA聚合酶亚基α有有限的同源性（宋，C.Z.，花田，K.，矢野，K.，前田，Y.，山本，K.，和村松，M.（1994）《生物化学杂志》269，26976 - 26981）。在这项研究的扩展中，我们现在通过酵母双杂交系统，以mRPA40作为诱饵，克隆出了编码小鼠RNA聚合酶I 16 kDa亚基的小鼠RPA16（mRPA16）cDNA。推导的氨基酸序列与已知与AC40相关的RNA聚合酶I和III的酵母亚基AC19有45%的同一性，并且与细菌α亚基有局部相似性。我们已经表明，mRPA40突变体无法与mRPA16相互作用，并且在酵母双杂交系统中，mRPA16和mRPA40自身都不能相互作用。这些结果表明，高等真核生物的RNA聚合酶I保留了两个不同的α相关亚基，它们在RNA聚合酶I组装的早期阶段相互作用。
