TFIIA induces conformational changes in TFIID via interactions with the basic repeat.

Abstract

. Components of the general transcription machinery are functionally conserved among eukaryotes, as evidenced by the ability of TFIIA and TFIID from Saccharomyces cerevisiae to substitute for the corresponding HeLa factors in vitro (2,4,14,21). TFIID binding to the TATA element initiates the assembly of the other factors into a preinitiation complex (1,34,54,55). Yeast TFIID (yTFIID) and the TATA-binding subunit of TFIID (designated TFIIDT or TBP) from higher eukaryotes contain a highly conserved 180-amino-acid C-terminal domain and divergent N-terminal regions (3, 8, 11, 15-18, 22, 25, 33, 35, 47, 52). Biochemical and genetic studies have shown that the conserved C-terminal domain of TFIID'T contains all of the essential regions for DNA binding, transcription initiation, and species specificity (6,13,23,36,40,56,57). TFIID shows unusual binding properties compared with those of the other sequence-specific DNA binding proteins: e.g., a temperature dependency and slow on and off rates (20,28,48).The binding of TFIID to DNA can be stimulated by TFIIA, apparently by direct interactions of TFIIA with TFIID (1, 30). The ability of TFIIA to interact directly with TFIID has allowed efficient purification of this protein from both HeLa cells (7, 7a, 53) and S. cerevisiae (38). TFIIA has been shown to function at an early step in the formation of a preinitiation complex (10,41). In contrast to the absolute requirement for the other transcription factors, a consistent requirement for TFIIA in the initiation of transcription has not been observed (for a review, see reference 42). This may reflect the nature of the TFIID-employed cross-contamination of factors, the presence of alternative factors, or the * Corresponding author. particular conditions of transcription (1, 7, 31, 32, 41-45, 51, 55). For example, the transcription factor TFIIG initially was identified as a factor which substitutes for TFIIA in basal transcription and which further stimulates TFIIAsaturated transcription (51). The initiator-binding transcription factor TFII-I (43) has been shown to substitute for TFIIA in transcription of the adenovirus major late (AdML) core promoter, suggesting alternative pathways for the formation of preinitiation complexes, possibly with different rates of formation and/or complex stabilities (for a review, see reference 42; 42a). The function(s) of TFIIA in preinitiation complex formation and transcription initiation has yet to be elucidated.Interactions of negative cofactors which bind competitively with TFIIA to TFIID on DNA have also been reported elsewhere (31,32). These negative cofactors dissociate TFIIA or TFIIB from the intermediary preinitiation complexes to produce nonproductive preinitiation complexes (negative cofactor-TFIID-DNA complexes) that result in repressed promoter states (for a review, see reference 42). Preincubation of promoters with TFIIA and native TFIID was shown to increase basal levels of transcription with corresponding decreases in promoter stimulation by activators, suggesting the involvem...

Multiple regions of TBP participate in the response to transcriptional activators in vivo.

“…4 and 5) were disrupted by individual sets of point mutations that had little if any effect in vivo. It is known that defects in DNA binding by yeast TBP can be overcome in vivo and during in vitro basal transcription (Cormack and Struhl 1992;Lee et al 1992;Schultz et al 1992;Yamamoto et al 1992).…”

Molecular cloning of the small (gamma) subunit of human TFIIA reveals functions critical for activated transcription.

“…TFIIA is thought to be required for early steps in the assembly of an active preinitiation complex Maldonado et al 1990;Wang et al 1992;Lieberman and Berk 1994). TFIIA binds directly to TBP and stabilizes the interaction of TBP with the TATA box in electrophoresis mobility shift assays (EMSA) Maldonado et al 1990; Lee et al 1992;Imbalzano et al 1994). The binding of TFIIA to TBP alters the DNA-binding properties of TBP and is likely to contribute to changes in promoter recognition and transcriptional activity (Lee et al 1992).…”

“…TFIIA binds directly to TBP and stabilizes the interaction of TBP with the TATA box in electrophoresis mobility shift assays (EMSA) Maldonado et al 1990; Lee et al 1992;Imbalzano et al 1994). The binding of TFIIA to TBP alters the DNA-binding properties of TBP and is likely to contribute to changes in promoter recognition and transcriptional activity (Lee et al 1992). TFIIA was also required during a preincubation of TFIID with activator to overcome a rate-limiting step in open complex formation (Wang et al 1992;Chi and Carey 1993).…”

Self-association of the Amino-terminal Domain of the Yeast TATA-binding Protein

“…It binds TATA sequence DNA as a monomer (21-26) and interacts with TAFs and general transcription factors as a monomer (13,14,(27)(28)(29). On the other hand, TBP is capable of selfassociation.…”