Transcription factor II D ( TF II D ) is one of several general transcription factors that make up the RNA polymerase II preinitiation complex . RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein -coding genes in living cells. It consists of RNA polymerase II , a subset of general transcription factors , and regulatory proteins known as SRB proteins. Before the start of transcription , the transcription Factor II D (TF II D) complex binds to the core promoter DNA of the gene through specific recognition of promoter sequence motifs, including the TATA box , Initiator , Downstream Promoter , Motif Ten, or Downstream Regulatory elements.
2-513: TF II D is itself composed of TBP and several subunits called TATA-binding protein Associated Factors ( TBP-associated factors , or TAFs ). In a test tube, only TBP is necessary for transcription at promoters that contain a TATA box . TAFs, however, add promoter selectivity, especially if there is no TATA box sequence for TBP to bind to. TAFs are included in two distinct complexes, TF II D and B-TF II D. The TF II D complex
4-460: Is composed of TBP and more than eight TAFs. But, the majority of TBP is present in the B-TF II D complex, which is composed of TBP and TAFII170 ( BTAF1 ) in a 1:1 ratio. TF II D and B-TF II D are not equivalent, since transcription reactions utilizing TF II D are responsive to gene specific transcription factors such as SP1, while reactions reconstituted with B-TF II D are not. Subunits in
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