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 593-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.