Myers Lawrence C, Lacomis Lynne, Erdjument-Bromage Hediye, Tempst Paul
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA.
Mol Cell. 2002 Oct;10(4):883-94. doi: 10.1016/s1097-2765(02)00644-5.
Using a highly pure transcription system derived from Saccharomyces cerevisiae, we have purified an activity in yeast whole-cell extracts that represses RNA polymerase II transcription. Mechanistic studies suggest that this repressor specifically targets transcriptional reinitiation. The two polypeptides that constitute the repressor have been identified as Ceg1p and Cet1p, the two subunits of the yeast pre-mRNA capping enzyme. A purified recombinant capping enzyme is able to reconstitute repressor activity. Cet1p is necessary for and capable of this repression. Transcriptional run-on experiments indicate that the capping enzyme also serves as a repressor in vivo. Efficient pre-mRNA capping relies on interactions between the capping enzyme and transcription apparatus. Repression by the capping enzyme suggests a bidirectional flow of information between capping and transcription.
利用源自酿酒酵母的高度纯化转录系统，我们在酵母全细胞提取物中纯化出一种可抑制RNA聚合酶II转录的活性物质。机制研究表明，这种阻遏物特异性靶向转录重新起始。构成该阻遏物的两种多肽已被鉴定为酵母前体mRNA加帽酶的两个亚基Ceg1p和Cet1p。纯化的重组加帽酶能够重建阻遏物活性。Cet1p对于这种抑制是必需的且能够实现这种抑制。转录延伸实验表明，加帽酶在体内也起到阻遏物的作用。高效的前体mRNA加帽依赖于加帽酶与转录装置之间的相互作用。加帽酶的抑制作用表明加帽与转录之间存在双向信息流。
