Human transcription factor IIIC box B bindingsubunit.

Abstract

Transcription factor HIC (TFIC) is a multisubut basic TF for RNA polymerase m. It initiates transcriptin complex assembly on tRNA and related genes by binding to the internal box B promoter element and is also required for transcription ofSS rRNA In contrast to the yeast system, activities in a partially purified human TFIIIC fraction required for tRNA transcription separate into two components called TFIIIC1 and TF-IIIC2 (11). RNA pol III TFs from Bombxy mori also resolve into several components including two activities separated from a partially purified TFIIIC fraction called TFIIIC and TRIIID (12). The human TFIIIC2 fraction most closely resembles yeast TFIIIC in that it also binds to the box B promoter element with high affinity (11,13,14), can stably sequester a template (15), and is a multisubunit protein composed of five copurifying polypeptides of 230, 110, 100, 80, and 60 kDa (14,16,17). In both the yeast and human systems, the largest polypeptide can be specifically crosslinked to box B DNA (13,(16)(17)(18). Because the protein we have referred to as TFIIIC2 (16) 1652The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Cloning and characterization of a TFIIIC2 subunit (TFIIIC beta) whose presence correlates with activation of RNA polymerase III-mediated transcription by adenovirus E1A expression and serum factors.

“…Consistent with these findings, anti-TFIIIC6 antibodies failed to detect any immunologically related proteins in yeast extracts. Hence, although at least some components (TBP and RNA polymerase subunits) of the RNA polymerase III transcription machinery show substantial sequence conservation between yeast and human (Hernandez 1993;Ittmann et al 1993) the present and past (L'Etoile et al 1994;Lagna et al 1994) observations point either to a functional convergence or to a low sequence conservation in TFIIIC subunits. However, as discussed below, it is likely that human counterparts to some of the yeast TFIIIC components most likely reside in the as yet uncharacterized TFIIIC1 subunits, and sequences for some of the yeast TFIIIC subunits have not yet been reported.…”

“…The TFIIIC[3 amino acid sequence was compared with sequences from the 220-kD human (L'Etoile et al 1994) and rat {Lagna et al 1994) TFIIIC~ subunit and with the 95-kD (TFCI: Swanson et al 1991, Parson andWeil 1992), 131-kD (TFC4: Marck et al 1993), and 138-kD (TFC3: Lefebvre et al 1992) subunits of yeast TFIIIC and no significant sequence similarities were found. Consistent with this analysis anti-TFIIIC~ antibody failed to react on a Western blot with any polypeptide of partially purified yeast TFIIIC (data not shown).…”

“…or by SDS-PAGE analysis after immunoprecipitation with anti-TFIIIC(x antibodies (L'Etoile et al 1994;Lagna et al 1994). In contrast, the 77-kD polypeptide has copurified consistently with TFIIIC2b, although it has not been detected by immunoprecipitation with anti-TFIIICoL antibodies (which might have resulted in its dissociation) (L'Etoile et al 1994;Lagna et al 1994). On the basis of these analyses, we conclude that TFIIIC2a contains subunits of 220, 110, 102, 90, and 63 kD, whereas TFIIIC2b differs with respect to the absence of the 110-kD subunit and the possible presence of a substitute 77-kD subunit.…”

“…Roeder, unpubl.). The failure to detect these novel polypeptides in previous preparations of chromatographically purified TFIIIC2a (Yoshinaga et al 1989;Kovelman and Roeder 1992) most likely reflects their dissociation and separation using these purification procedures, and their apparent absence in anti-TFIIICc~ immunoprecipitates (L'Etoile et al 1994;Lagna et al 1994) may have resulted from their dissociation from TFIIIC2a by the antibodies used. In the present analysis the quantitative removal of TFIIIC1 activity from nuclear extracts with an antibody (anti-TFIIIC~) specific for TFIIIC2a further suggests that TFIIIC1 is not associated with the inactive form (TFIIIC2b) of TFIIIC2 and that TFIIICB could play a direct role in stabilizing interactions of TFIIIC2a with TFIIIC1.…”

Isolation and Cloning of Four Subunits of a Fission Yeast TFIIIC Complex That Includes an Ortholog of the Human Regulatory Protein TFIIICβ

“…By contrast to these initiation factors, the downstream TFIIIC subunits in these organisms had revealed no recognizable sequence relatedness. For example, hTFIIIC220, the human polypeptide that binds the B box, bears no homology to the S. cerevisiae B box-binding factor, TFC3p, or to anything in the S. cerevisiae sequence data base (22,23). 2 Some S. cerevisiae TFIIIC subunits, TFC7p and TFC8p, as well as the downstream protein, TFC6p, were reported to have no human homologs (13,(25)(26)(27).…”