TFIIIC

TFIIIC subunits TFIIIC90 and TFIIICllO. The known function of TFIIIC is to initiate transcription complex formation by binding to promoter DNA and recruiting TBP-containing TFIIIB and RNA polymerase III, that directs synthesis of tRNA precursors. TFIIIC have an intrinsic HAT activity. 

After TFIIIA binds, proteins TFIIIC and then TFII-IB also bind. Although promoters of classes 2 and 3 do not require TFIIIA, all three classes depend upon TFIIIB and TFIIIC.484 The TATA-binding protein TBF is one of three components present in TFIIIB, which may be regarded as the true initiation factor.47 485 Both TFIIIA and TFIIIC can be described as assembly factors 47 A silkworm RNA pol III has been reported to require a transcription factor consisting of RNA 486... 

Eukaryotic cells contain multiple copies of the 5S rRNA gene. Unlike other eukaryotic rRNA genes, the 5S rRNA genes are transcribed by RNA Pol III. Two control elements, an A box and a C box, lie downstream of the transcriptional start site. The C box binds TFIIIA which then recruits TFIIIC. TFIIIB now binds and interacts with RNA Pol III to form the transcription initiation complex. Transcription produces a mature 5S rRNA that requires no processing. 

In eukaryotes, the tRNA genes exist as multiple copies and are transcribed by RNA polymerase III (RNA Pol III). As in prokaryotes, several tRNAs may be transcribed together to yield a single pre-tRNA molecule that is then processed to release the mature tRNAs. The promoters of eukaryotic tRNA genes are unusual in that the transcriptional control elements are located downstream (i.e. on the 3 side) of the transcriptional start site (at position +1). In fact they lie within the gene itself. Two such elements have been identified, called the A box and B box (Fig. 3). Transcription of the tRNA genes by RNA Pol III requires transcription factor IIIC (TFIIIC) as well as TFIIIB. THIIC binds to the A and B boxes whilst TFIIIB binds upstream of the A box. TFIIIB contains three subunits, one of which is TBP (TATA binding protein), the polypeptide required by all three eukaryotic RNA polymerases. 

Three general transcription factors are required for Pol III to Initiate transcription of tRNA and SS-rRNA genes In vitro. Two multimeric factors, TFIIIC and TFIIIB, participate In Initiation at both tRNA and SS-rRNA promoters a third factor, TFIIIA, Is required for initiation at SS-rRNA promoters. As with assembly of Pol I and Pol II Initiation complexes, the Pol III general transcription factors bind to promoter DNA in a defined sequence. 

S Ribosomal RNA genes - The most thoroughly studied genes transcribed by RNA polymerase III are those for 5S ribosomal RNA. At least three protein factors in addition to polymerase III are needed for the expression of the 5S rRNA genes in vitro. Two of these transcription factors (TFIIIB and TFIIIC) appear to participate in the transcription of tRNA genes as well, but one (called TFIIIA) is specific for the 5S genes. 

II. Brfl-TFIIIC A Limiting Interaction in Preinitiation Complex Assembly. 95... 

VI. Ordered Binding of TFIIIB Subunits to TFIIIC-DNA and Dynamic... 

This chapter focuses on recent advances in our understanding of a critical limiting step in Pol III transcription the assembly on DNA of the initiation factor TFIIIB by TFIIIC. 

Bartholomew, B., Kassavetis, G. A., and Geiduschek, E. P. (1991). Two components of Saccharomyces cerevisiae transcription factor IIIB (TFIIIB) are stereospecifically located upstream of a tRNA gene and interact with the second-largest subunit of TFIIIC. Mol. Cell. Biol. 11, 5181-5189. 

Chaussivert, N., Conesa, C., Shaaban, S., and Sentenac, A. (1995). Complex interactions between yeast TFIIIB and TFIIIC. J. Biol. Chem. 270, 15353-15358. 

Dieci, G., Percudani, R., Giuliodori, S., Bottarelli, L., and Ottonello, S. (2000). TFIIIC independent in vitro transcription of yeast tRNA genes. / Mol. Biol. 299, 601-613. 

Dumay-Odelot, H., Acker, J., Arrebola, R., Sentenac, A., and Marek, C. (2002). Multiple roles of the taul31 subunit of yeast transcription factor IIC (TFIIIC) in TFIIIB assembly. Mol. Cell. Biol. 22, 298-308. 

Hsieh, Y. J., Kundu, T. K., Wang, Z., Kovelman, R., and Roeder, R. G. (1999a). The TFIIIG90 subunit of TFIIIC interacts with multiple components of the RNA polymerase III machinery and contains a histone-specific acetyltransferase activity. Mol. Cell. Biol. 19, 7697-7704. 

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