Transcription by RNA polymerase III (pol III) is a complex molecular process orchestrated by the two main transcription factors, TFIIIB and TFIIIC. The TFIIIB complex can be recruited by TFIIIC to upstream DNA and form an exceptionally kinetically stable TFIIIB-DNA complex, which then recruits the Pol III enzymatic complex and helps maintain it for multiple transcription cycles in a process called facilitated recycling []. Saccharomyces cerevisiae TFIIIB is a complex of three subunits, the TATA box-binding protein TBP, the TFIIB-related factor BRF, and the beta'' protein. This entry represents transcription factor IIIB subunit Brf1, which is a homologue of the functionally analogous pol II initiation factor, TFIIB []. In budding yeast, Brf1 interacts with several initiation-specific subunits of the pol III machinery, TBP, beta", TFC4p and the pol III subunits C34 and C17 [].
In budding yeasts, Brf1 forms the TFIIIB complex with TATA-binding protein (TBP) and Bdp1 []. The TFIIIB complex can be recruited to the Pol III promoters and form an exceptionally kinetically stable TFIIIB-DNA complex, which then recruits the Pol III enzymatic complex and helps maintain it for multiple transcription cycles in a process called facilitated recycling [].This entry represents the TATA binding protein (TBP) binding domain of Brf1 that covers both the Brf homology II and III regions [].
In eukaryotes, transcription initiation by polymerase II is modulated by both general and specific transcription factors. The general factors (which include TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIG and TFIIH) operate through common promoter elements, such as the TATA box. Transcription factor IIB (TFIIB) is of central importance in transcription of class II genes. It associates with TFIID-TFIIA bound to DNA (the DA complex) to form a ternary TFIID-IIA-IBB (DAB) complex, which is recognised by RNA polymerase II [, ]. TFIIB comprises ~315-340 residues and contains an imperfect C-terminal repeat of a 75-residue domain that may contribute to the symmetry of the folded protein.Proteins in this entry also include transcription factor IIIB subunit Brf1, which shares protein sequence similarity with TFIIB. In budding yeast, Brf1 interacts with several initiation-specific subunits of the pol III machinery, TBP, beta", TFC4p and the pol III subunits C34 and C17 [].
