The TFIID Components Human TAF_II140 andDrosophila BIP2 (TAF_II155) Are Novel Metazoan Homologues of Yeast TAF_II47 Containing a Histone Fold and a PHD Finger

Abstract

The RNA polymerase II transcription factor TFIID comprises the TATA binding protein (TBP) and a set of TBP-associated factors (TAF II s). TFIID has been extensively characterized for yeast, Drosophila, and humans, demonstrating a high degree of conservation of both the amino acid sequences of the constituent TAF II Transcription factor TFIID is one of the general factors required for accurate and regulated initiation by RNA polymerase II. TFIID comprises the TATA binding protein (TBP) and TBP-associated factors (TAF II s) (3,24). A subset of TAF II s are present not only in TFIID but also in the SAGA, PCAF, STAGA, and TFTC complexes (5,16,22,33,38,53).The function of TAF II s has been studied using in vitro transcription systems which have provided evidence that they act as specific coactivators by interacting directly with transcriptional activator proteins (48). Such studies also indicated that TAF II s contribute to promoter recognition and promoter selectivity (8,10,49). Genetic evidence obtained from TAF II knockout and depletion experiments and temperature-sensitive (TS) mutants indicates that TAF II s are involved in the control of gene expression in yeast and mammalian cells and that they act as antiapoptotic factors (11, 23, 37; for reviews, see references 2, 3, and 23).TFIID has been characterized for Drosophila, humans, and yeast (7,14,40,56). After its initial purification, many subunits were rapidly identified and the corresponding genes were cloned. Sequence comparisons allowed the identification of TAF II s in each species sharing one or more conserved domains. Many of these domains correspond to structural motifs, such as the histone fold domain (HFD), the ␤-transducin repeat, and bromodomain, or catalytic domains, such as the histone acetyltransferase domain. These results indicate that the composition and organization of TFIID has been well conserved between yeast and humans (reviewed in reference 16).In recent years, it has been assumed that all the mammalian TFIID components have been identified. Several observations, however, challenge this assumption. Characterization of highly purified yeast TFIID (yTFIID) has identified two novel TFIID subunits, yTAF II 48 (Mpt1) and yTAF II 65 (42,45

Functional Analysis of the TFIID-specific Yeast TAF4 (yTAFII48) Reveals an Unexpected Organization of Its Histone-fold Domain

“…Biochemical studies have also indicated that yTAF3 and yTAF8 contain HFDs that heterodimerize with a HFD in yTAF10 (33). A similar result was obtained in studies of their metazoan orthologues (21,34). The existence of these heterodimers in native yeast TFIID is supported by immunoelectron microscopy, which shows colocalization of these proteins (31).…”

Two Distinct Roles of ARABIDOPSIS HOMOLOG OF TRITHORAX1 (ATX1) at Promoters and within Transcribed Regions of ATX1-Regulated Genes

“…In the case of MLL1, loss of MLL1 affects Pol II occupancy at target genes, possibly through a mechanism involving binding of H3K4me3 by the PHD domain of the TAF3 subunit of TFIID (Vermeulen et al, 2007). Interestingly, Arabidopsis lacks a TAF3 subunit (Lawit et al, 2007) and yeast TAF3 lacks a PHD finger (Gangloff et al, 2001), indicating that TAF3 tethering of PIC to H3K4me3 nucleosomes is not a general mechanism in all organisms. In further support of this difference, treatment with Flap or Selic CDK7/CDK9 inhibitors reduced H3K4me3 levels without reducing TBP occupancy at the three ATX1-dependent promoters examined ( Figure 7B).…”

The YPWM motif links Antennapedia to the basal transcriptional machinery

“…Based on the strict requirement of the YPWM motif to transform an eye into a wing, we screened for YPWM-motifspecific interacting co-factors. Employing the yeast two-hybrid system, we identified a novel Antp co-factor bric-à-brac interacting protein 2 (bip2), also referred to as dTAFII3 or TAFII155 (Gangloff et al, 2001), which specifically interacts with the YPWM motif of Antp in vitro and in vivo. Using gain-and loss-of-function approaches, we show that bip2 genetically interacts with Antp promoting dorsal ectopic wing development…”