Chiannilkulchai N, Moenne A, Sentenac A, Mann C
Service de Biochimie et Génétique Moléculaire, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
J Biol Chem. 1992 Nov 15;267(32):23099-107.
RPC53 has previously been shown to encode an essential subunit required for tRNA gene transcription by RNA polymerase C in vivo (Mann, C., Micouin, J.-Y., Chiannilkulchai, N., Treich, I., Buhler, J.-M., and Sentenac, A. (1992) Mol. Cell. Biol. 12, in press). In this paper, we have determined that an unusual rho+ lethality associated with the rpc53::HIS3-1 disruption mutation is due to the inadvertent formation of a Pet56-C53 fusion protein. This fusion protein is missorted to mitochondria, thereby reducing the quantity of the C53 subunit available for RNA polymerase C assembly. We show that the carboxyl-terminal region of C53 contains the essential functional domain of the subunit and that a mutant RNA polymerase containing only this domain is thermolabile for its function in vivo and in vitro. The thermolability of the carboxyl-terminal C53 domain is suppressed by five different genes on multicopy plasmids, including RPC160, encoding the largest subunit of RNA polymerase C and SSD1/SRK1, which has been implicated in the activity of protein phosphatases.
此前已有研究表明，RPC53编码一种体内RNA聚合酶C转录tRNA基因所需的必需亚基（曼恩，C.，米库安，J.-Y.，钱尼尔库尔猜，N.，特雷希，I.，比勒，J.-M.，和森特纳克，A.（1992年）《分子与细胞生物学》12卷，即将发表）。在本文中，我们确定与rpc53::HIS3-1破坏突变相关的一种异常的rho+致死性是由于意外形成了Pet56-C53融合蛋白。这种融合蛋白被错误分选到线粒体中，从而减少了可用于RNA聚合酶C组装的C53亚基的数量。我们表明，C53的羧基末端区域包含该亚基的必需功能域，并且仅包含该结构域的突变RNA聚合酶在体内和体外的功能对温度敏感。羧基末端C53结构域的温度敏感性被多拷贝质粒上的五个不同基因抑制，包括编码RNA聚合酶C最大亚基的RPC160和与蛋白磷酸酶活性有关的SSD1/SRK1。
