Conserved region I of human coactivator TAF4 binds to a short hydrophobic motif present in transcriptional regulators

Abstract

TBP-associated factor 4 (TAF4), an essential subunit of the TFIID complex acts as a coactivator for multiple transcriptional regulators, including Sp1 and CREB. However, little is known regarding the structural properties of the TAF4 subunit that lead to the coactivator function. Here, we report the crystal structure at 2.0-Å resolution of the human TAF4-TAFH domain, a conserved domain among all metazoan TAF4, TAF4b, and ETO family members. The hTAF4-TAFH structure adopts a completely helical fold with a large hydrophobic groove that forms a binding surface for TAF4 interacting factors. Using peptide phage display, we have characterized the binding preference of the hTAF4-TAFH domain for a hydrophobic motif, D⌿⌿ ⌿⌽, that is present in a number of nuclear factors, including several important transcriptional regulators with roles in activating, repressing, and modulating posttranslational modifications. A comparison of the hTAF4-TAFH structure with the homologous ETO-TAFH domain reveals several critical residues important for hTAF4-TAFH target specificity and suggests that TAF4 has evolved in response to the increased transcriptional complexity of metazoans.TFIID ͉ transcription ͉ x-ray crystallography ͉ TAFH domain T he general transcription factor TFIID, composed of the TATAbinding protein (TBP) and at least 14 additional TBPassociated factors (TAFs) (1), plays an important role in the regulation of gene transcription by RNA polymerase II. It contributes to a large number of activities necessary for regulated transcription, such as core promoter recognition and chromatin modification and recognition (2, 3). Individual TAFs are important for mediating distinct activator-specific transcriptional regulation in vivo (4). Studies of yeast strains having temperature-sensitive mutations indicate that Ϸ84% of yeast genes depend on one or more TAFs (5), indicating the importance of this factor in RNA Pol II transcription.The human TAF4 (hTAF II 130/dTAF II 110) subunit of the TFIID complex was the first of the TAF subunits demonstrated to possess coactivator activity for the glutamine-rich activators Sp1 (6), CREB (7), and nuclear receptors RAR and TR (8). More recently, TAF4 has been demonstrated to play a critical role in maintaining the stability of the TFIID complex (9). The hTAF4 sequence contains four glutamine-rich tracts mediating interactions with the activators Sp1 and CREB (7) and two highly conserved domains CI and CII [supporting information (SI) Fig. 5A]. The misregulation of Sp1 activation mediated by hTAF4 has been implicated in Huntington's disease and a number of other neurodegenerative diseases that result from polyglutamine expansions (10). A region (residues 870-911) of the CII domain has been shown to interact with the histone-fold motif of hTAF12 and form a novel histone-like pair (11). The CI region of hTAF4 is highly conserved among all metazoan TAF4, TAF4b, and ETO family members and is also known as the TAF homology (TAFH) domain (6, 12) (SI Fig. 5B). The ETO-TAFH domain has been demonstrated t...

A TAF4 coactivator function for E proteins that involves enhanced TFIID binding

“…These results suggest that, despite their high degree of similarity, eTAFH and dTAFH domains may act mainly through distinct binding partners. In agreement with these observations, the two TAFH domains exhibit structural differences that likely affect their binding specificity (Plevin et al 2006;Wang et al 2007). Notably, in relation to alternative HEB interactions, the AD1-eTAFH interaction facilitates repression of HEB target genes by both blocking AD1-p300 interactions (below) and effecting corepressor ETO (and associated HDAC) recruitment to HEB target genes (Zhang et al 2004), while the AD3-dTAFH interaction facilitates activation of HEB target genes by TAF4/TFIID recruitment.…”

“…These results strongly suggest that the TAFH domain plays a crucial role in a broad range of activator-TAF4/TFIID interactions. In support of this notion, a recent phage display screen for dTAFH-interacting peptides identified sequences resident in several known activators (Wang et al 2007), and a study in Drosophila revealed that a broad region of TAF4 containing the dTAFH domain interacts with Pygopus and is required by an unknown mechanism for Wingless-induced activation of the nkd gene by Pygopus (Wright and Tjian 2009).…”

Mammalian SWI/SNF-A Subunit BAF250/ARID1 Is an E3 Ubiquitin Ligase That Targets Histone H2B

“…1C). His-Elo C bound specifically to GST-BAF250bCTD and not to the control GST-TAFH protein (37), indicating that the observed interaction between Elo C and BAF250bCTD is not mediated by another protein(s) in mammalian cells. Thus, the bioinformatics, immunoprecipitation, and GST pulldown data support the mass spectrometry result and indicate that Elo C interacts with the CTD of BAF250.…”

Promoting developmental transcription

“…REVIEW Development 137 (1) TFIID to core promoters. For example, the glutamine-rich activation domains of the transcription factors Sp1 and CREB associate with Drosophila TAF4, but strong evidence that TAF-transcription factor interactions take place in vivo in the context of TFIID has been elusive (Wang et al, 2007). Thus, TAF interactions with modified histones and transcription factors might stabilize TFIID-core promoter interactions that are specified by the binding of TAFs to core promoter elements.…”