Mapping histone fold TAFs within yeast TFIID

Abstract

The transcription factor TFIID is a large multiprotein complex, composed of the TATA box-binding protein (TBP) and 14 TBP-associated factors (TAFs), which plays a key role in the regulation of gene expression by RNA polymerase II. The three-dimensional structure of yeast (y) TFIID, determined at~3 nm resolution by electron microscopy and image analysis, resembles a molecular clamp formed by three major lobes connected by thin linking domains. The yTFIID is structurally similar to the human factor although the clamp appears more closed in the yeast complex, probably re¯ecting the conformational¯exibility of the structure. Immunolabelling experiments showed that nine TAFs that contain the histone fold structural motif were located in three distinct substructures of TFIID. The distribution of these TAFs showed that the previously reported pair-wise interactions between histone fold domain (HFD)-containing TAFs are likely to occur in the native yTFIID complex. Most of the HFD-containing TAFs have been found in two distinct lobes, thus revealing an unexpected and novel molecular organization of TFIID.

Molecular and Genetic Characterization of a Taf1p Domain Essential for Yeast TFIID Assembly

“…These experiments showed that not all the TFIID-specific Tafps coprecipitated with Taf1p-region 4: for example, Taf1p, Taf2p, and Taf8p were not detected in these immunoprecipitates. We also note that no such dimer has yet been detected for yeast TFIID by co-IP (14,62), TFIID molecular sizing (62), or electron microscopy (39,40).…”

“…24,2004 SCAFFOLD FUNCTION OF Taf1p IN TFIID ASSEMBLY 4937 TFIID complex has emerged. New TFIID-specific Tafps have been identified (33,34,60,65,75), novel Tafp-Tafp interactions have been described (22,23,63,66,81), and low-resolution three-dimensional structures of the TFIID complex have been determined (2,11,39,40,48). In this study, we have performed a comprehensive analysis of all the TFIID components associated with Taf1p using co-IP assays and our family of Taf1p deletion mutants that encompass the entire TAF1 ORF.…”

“…Both human and yeast TFIID display a trilobed structure (2,11,39), and the HFD-containing Tafps have been mapped to these lobes (39). Based upon our data, TFIID assembly can be considered either as a cooperative process that is nucleated on Taf1p or as a modular process where a subcomplex composed of TBP, Taf1p, and Taf7p associates with another subcomplex(es), perhaps comprised of the remaining Tafps binding either pairwise as dimers (i.e., HFD TafX -HFD TafY ) (39) or as a Taf-octamer-like core (66).…”

“…However, a systematic Taf1p-Tafp interaction analysis of TFIID has yet to be reported. Yeast Taf1p shares extensive structural and functional similarities with its metazoan orthologs, and the TFIIDs isolated from both yeast and metazoan cells display very similar trilobed structures in electron microscopy studies (2,11,39). However, despite these many conserved properties, a similar scaffold function for yeast Taf1p has been disputed (1, 60).…”

Régulation de la transcription par le coactivateur TFIID

“…Figure 1A) [6]. L'utilisation d'anticorps a permis de positionner les différents TAF dans la structure de TFIID [7]. Les positions de TBP et de TAF2, tous deux impliqués dans la liaison avec le promoteur, ainsi que celle de l'extrémité amino-terminale de TAF1, qui comprend les motifs inhibiteurs TAND, ont été déterminées ( Figure 1A).…”