Previous Article | Next Article ![]()
Mol. Cell. Biol., Apr 1997, 1868-1880, Vol 17, No. 4
A Kumar, GA Kassavetis, EP Geiduschek, M Hambalko and CJ Brent
Transcription factor IIIB (TFIIIB), the central transcription factor of
Saccharomyces cerevisiae RNA polymerase III, is composed of TATA- binding
protein, the TFIIB-related protein Brf, and B". B", the last component to
enter the TFIIIB-DNA complex, confers extremely tight DNA binding on
TFIIIB. Terminally and internally deleted B" derivatives were tested for
competence to form TFIIIB-DNA complexes by TFIIIC- dependent and
-independent pathways on the SUP4 tRNA(Tyr) and U6 snRNA (SNR6) genes,
respectively, and for transcription. Selected TFIIIB- TFIIIC-DNA complexes
assembled with truncated B" were analyzed by DNase I footprinting, and the
surface topography of B" in the TFIIIB-DNA complex was also analyzed by
hydroxyl radical protein footprinting. These analyses define functional
domains of B" and also reveal roles in start site selection by RNA
polymerase III and in clearing TFIIIC from the transcriptional start.
Although absolutely required for transcription, B" can be extensively
truncated. Core proteins retaining as few as 176 (of 594) amino acids
remain competent to transcribe the SNR6 gene in vitro. TFIIIC-dependent
assembly on DNA and transcription requires a larger core of B": two domains
(I and II) that are required for SNR6 transcription on an either-or basis
are simultaneously required for TFIIIC-dependent assembly of DNA complexes
and transcription. Domains I and II of B" are buried upon assembly of the
TFIIIB-DNA complex, as determined by protein footprinting. The picture of
the TFIIIB-DNA complex that emerges is that B" serves as its scaffold and
is folded over in the complex so that domains I and II are near one
another.
Copyright © 1997, American Society for Microbiology
Functional dissection of the B" component of RNA polymerase III transcription factor IIIB: a scaffolding protein with multiple roles in assembly and initiation of transcription
Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla 92093-0634, USA.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|