Two Novel Drosophila TAF_IIs Have Homology with Human TAF_II30 and Are Differentially Regulated during Development

ABSTRACT

TFIID is a multiprotein complex composed of the TATA binding protein (TBP) and TBP-associated factors (TAF_IIs). The binding of TFIID to the promoter is the first step of RNA polymerase II preinitiation complex assembly on protein-coding genes. Yeast (y) and human (h) TFIID complexes contain 10 to 13 TAF_IIs. Biochemical studies suggested that the Drosophila (d) TFIID complexes contain only eight TAF_IIs, leaving a number of yeast and human TAF_IIs (e.g., hTAF_II55, hTAF_II30, and hTAF_II18) without knownDrosophila homologues. We demonstrate thatDrosophila has not one but two hTAF_II30 homologues, dTAF_II16 and dTAF_II24, which are encoded by two adjacent genes. These two genes are localized in a head-to-head orientation, and their 5′ extremities overlap. We show that these novel dTAF_IIs are expressed and that they are both associated with TBP and other bona fide dTAF_IIs in dTFIID complexes. dTAF_II24, but not dTAF_II16, was also found to be associated with the histone acetyltransferase (HAT) dGCN5. Thus, dTAF_II16 and dTAF_II24 are functional homologues of hTAF_II30, and this is the first demonstration that a TAF_II-GCN5-HAT complex exists inDrosophila. The two dTAF_IIs are differentially expressed during embryogenesis and can be detected in both nuclei and cytoplasm of the cells. These results together indicate that dTAF_II16 and dTAF_II24 may have similar but not identical functions.