Cloning, expression, and function of TFC5, the gene encoding the B" component of the Saccharomyces cerevisiae RNA polymerase III transcription factor TFIIIB.

TFC5, the unique and essential gene encoding the B" component of the Saccharomyces cerevisiae RNA polymerase III transcription factor (TF)IIIB has been cloned. It encodes a 594-amino acid protein (67,688 Da). Escherichia coli-produced B" has been used to reconstitute entirely recombinant TFIIIB that is fully functional for TFIIIC-directed, as well as TATA box-dependent, DNA binding and transcription. The DNase I footprints of entirely recombinant TFIIIB, composed of B", the 67-kDa Brf, and TATA box-binding protein, and TFIIIB reconstituted with natural B" are indistinguishable. A truncated form of B" lacking 39 N-terminal and 107 C-terminal amino acids is also functional for transcription. IMAGES:

已克隆得到酿酒酵母（Saccharomyces cerevisiae）RNA聚合酶III（RNA polymerase III）转录因子TFIIIB的B''组分编码基因TFC5，该基因为独特且必需的功能基因。其编码的蛋白含594个氨基酸残基，分子量为67688 Da。利用大肠杆菌（Escherichia coli）表达获得的B''组分，可重建得到完全重组型TFIIIB，该重组复合物可在受TFIIIC调控以及依赖TATA盒的DNA结合与转录反应中发挥完全功能活性。由B''组分、67 kDa的Brf以及TATA盒结合蛋白（TATA box-binding protein）组装而成的完全重组型TFIIIB，与使用天然B''组分重建得到的TFIIIB的DNase I足迹（DNase I footprint）实验结果无显著差异。一种截短形式的B''组分（缺失N端39个氨基酸与C端107个氨基酸）同样可支持转录反应的正常进行。图像：