TATA Binding Protein (TBP) Associated Factor 4 (TAF4) is one of several TAFs that bind TBP and is involved in forming Transcription Factor IID (TFIID) complex
The TATA Binding Protein (TBP) Associated Factor 4 (TAF4) is one of several TAFs that bind TBP and are involved in forming the Transcription Factor IID (TFIID) complex. TFIID is one of seven General Transcription Factors (GTF) (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIID) that are involved in accurate initiation of transcription by RNA polymerase II in eukaryote. TFIID plays an important role in the recognition of promoter DNA and assembly of the pre-initiation complex. TFIID complex is composed of the TBP and at least 13 TAFs. TAFs from various species were originally named by their predicted molecular weight or their electrophoretic mobility in polyacrylamide gels. A new, unified nomenclature for the pol II TAFs has been suggested to show the relationship between TAF orthologs and paralogs. Several hypotheses are proposed for TAFs functions such as serving as activator-binding sites, core-promoter recognition or a role in essential catalytic activity. Each TAF, with the help of a specific activator, is required only for the expression of subset of genes and is not universally involved for transcription as are GTFs. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID. Several TAFs interact via histone-fold (HFD) motifs; HFD is the interaction motif involved in heterodimerization of the core histones and their assembly into nucleosome octamers. The minimal HFD contains three alpha-helices linked by two loops and is found in core histones, TAFS and many other transcription factors. TFIID has a histone octamer-like substructure. TAF4 domain interacts with TAF12 and makes a novel histone-like heterodimer that binds DNA and has a core promoter function of a subset of genes.