TATA Binding Protein (TBP) Associated Factor 8The TATA Binding Protein (TBP) Associated Factor 8 (TAF8) is one of several TAFs that bind TBP, and is 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 eukaryotes. TFIID plays an important role in the recognition of promoter DNA and the assembly of the preinitiation complex. The 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, involvement in the core-promoter recognition, or a role in the essential catalytic activity of the complex. The mouse ortholog of TAF8 is called taube nuss protein (TBN), and is required for early embryonic development. TBN mutant mice exhibit disturbances in the balance between cell death and cell survival in the early embryo. TAF8 plays a role in the differentiation of preadipocyte fibroblasts to adipocytes; it is also required for the integration of TAF10 into the TAF complex. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID. TAF8 is also a component of a small TAF complex (SMAT), which contains TAF8, TAF10 and SUPT7L. Several TAFs interact via histone-fold motifs. The histone fold (HFD) is the interaction motif involved in heterodimerization of the core histones and their assembly into nucleosome octamer. TAF8 contains an H4 related histone fold motif, and interacts with several subunits of TFIID, including TBP and the histone-fold protein TAF10. Currently, five HF-containing TAF pairs have been described or suggested to exist in TFIID: TAF6-TAF9, TAF4-TAF12, TAF11-TAF13, TAF8-TAF10 and TAF3-TAF10.