Henry N L, Campbell A M, Feaver W J, Poon D, Weil P A, Kornberg R D
Department of Structural Biology, Stanford University School of Medicine, California 94305.
Genes Dev. 1994 Dec 1;8(23):2868-78. doi: 10.1101/gad.8.23.2868.
RNA polymerase transcription factor IIF (TFIIF) is required for initiation at most, if not all, polymerase II promoters. We report here the cloning and sequencing of genes for a yeast protein that is the homolog of mammalian TFIIF. This yeast protein, previously designated factor g, contains two subunits, Tfg1 and Tfg2, both of which are required for transcription, essential for yeast cell viability, and whose sequences exhibit significant similarity to those of the mammalian factor. The yeast protein also contains a third subunit, Tfg3, which is less tightly associated and at most stimulatory to transcription, dispensable for cell viability, and has no known counterpart in mammalian TFIIF. Remarkably, the TFG3 gene encodes yeast TAF30, and furthermore, is identical to ANC1, a gene implicated in actin cytoskeletal function in vivo (Welch and Drubin 1994). Tfg3 is also a component of the recently described mediator complex (Kim et al. 1994), whose interaction with the carboxy-terminal repeat domain of RNA polymerase II enables transcriptional activation. Deletion of TFG3 results in diminished transcription in vivo.
RNA聚合酶转录因子IIF（TFIIF）对于大多数（即便不是全部）聚合酶II启动子的起始过程都是必需的。我们在此报告了一种酵母蛋白基因的克隆和测序，该酵母蛋白是哺乳动物TFIIF的同源物。这种先前被命名为因子g的酵母蛋白包含两个亚基，即Tfg1和Tfg2，二者对于转录都是必需的，对酵母细胞的生存力至关重要，并且其序列与哺乳动物因子的序列表现出显著的相似性。该酵母蛋白还包含第三个亚基Tfg3，它与蛋白结合较松散，对转录最多起刺激作用，对于细胞生存力而言并非必需，并且在哺乳动物TFIIF中没有已知的对应物。值得注意的是，TFG3基因编码酵母TAF30，此外，它与ANC1相同，ANC1是一个在体内与肌动蛋白细胞骨架功能有关的基因（韦尔奇和德鲁宾，1994年）。Tfg3也是最近描述的中介体复合物的一个组分（金等人，1994年），该复合物与RNA聚合酶II的羧基末端重复结构域的相互作用能够实现转录激活。TFG3的缺失导致体内转录减少。
