Domains of the Brf component of RNA polymerase III transcription factor IIIB (TFIIIB): functions in assembly of TFIIIB-DNA complexes and recruitment of RNA polymerase to the promoter.
Saccharomyces cerevisiae transcription factor IIIB (TFIIIB) is composed of three subunits: the TATA-binding protein, the TFIIB-related protein Brf, and B". TFIIIB, which is brought to RNA polymerase III-transcribed genes indirectly through interaction with DNA-bound TFIIIC or directly through DNA recognition by the TATA-binding protein, in turn recruits RNA polymerase III to the promoter. N-terminally deleted derivatives of Brf have been examined for their ability to interact with DNA-bound TFIIIC and with the other components of TFIIIB and for participation in transcription. Brf(165-596), lacking 164 N-proximal TFIIB-homologous amino acids, is competent to participate in the assembly of TFIIIB-DNA complexes and in TFIIIC-independent transcription. Even deletion of the entire TFIIB-homologous half of the protein, as in Brf(317-596) and Brf(352-596), allows some interaction with DNA-bound TBP and with the B" component of TFIIIB to be retained. The function of Brf(165-596) in transcription has also been examined in the context of B" with small internal deletions. The ability of Brf with this sizable N-terminal segment deleted to function in TFIIIC-independent transcription requires segments of B" that are individually indispensable although required on an either/or basis, in the context of complete Brf. These findings suggest a functional complementarity and reciprocity between the Brf and B" components of TFIIIB.
Kassavetis
G A
GA
Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla 92093-0634, USA. gkassavetis@ucsd.edu
Bardeleben
C
C
Kumar
A
A
Ramirez
E
E
Geiduschek
E P
EP
D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012320:RNA Polymerase III / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors / Q000378:metabolism*
C090956:BRF1 protein, S cerevisiae; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; D004247:DNA; D012320:RNA Polymerase III