Human TAF(parallel to)105 is a cell type-specific TFIID subunit related to hTAF(parallel to)130

We previously characterized Drosophila and human TAF subunits that make up the core TFIID complex found in all cells. Here, we report that differentiated B cells contain a novel substoichiometric TAF of 105 kDa not found associated with TFIID isolated from other cell types. The cDNA encoding hTAF(II)105 reveals a highly conserved C-terminal domain shared by hTAF(II)130 and dTAF(II)110, while the N-terminal coactivator domain has diverged significantly. All cells tested express TAF(II)105 mRNA, but only B cells contain significant levels of protein associated with TFIID. Transient overexpression of hTAF(II)105 selectively squelches the transcription of some genes in B cells. These properties suggest that TAF(II)105 is a cell type-specific subunit of TFIID that may be responsible for mediating transcription by a subset of activators in B cells.