Function of TAFII-containing complex without TBP in transcription by RNA polymerase II

Abstract
Initiation of transcription of a gene from a core promoter region by RNA polymerase II requires the assembly of several initiation factors to form a preinitiation complex. Assembly of this complex1,2 is thought to be nucleated exclusively by the sequence-specific binding of the TFIID transcription factor complex, which is composed of the TATA-binding protein (TBP) and TBP-associated factors (TAFIIs) (refs 3, 4), to the different promoters. Here we isolate and characterize a new multiprotein complex that does not contain either TBP or a TBP-like factor but is composed of several TAFIIs and other proteins. This complex can replace TFIID on both TATA-containing and TATA-lacking promoters in in vitro transcription assays. Moreover, an anti-TBP antibody that inhibits TBP- and TFIID-dependent transcription does not inhibit activity of this new complex. These results indicate that TBP-free RNA polymerase II mediated transcription may be able to occur in mammalian cells and that multiple preinitiation complexes may play an important role in regulating gene expression.