Transcription factor II D

Transcription factor II D (TF_IID) 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 (TFIID) complex binds to the TATA box in the core promoter of the gene.

Functions

• Coordinates the activities of more than 70 polypeptides required for initiation of transcription by RNA polymerase II
• Binds to the core promoter to position the polymerase properly
• Serves as the scaffold for assembly of the remainder of the transcription complex
• Acts as a channel for regulatory signals

Structure

TF_IID is itself composed of 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.^[1] 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, TFIID^[2] and B-TFIID.^[3] The TFIID complex is composed of TBP and more than eight TAFs. But, the majority of TBP is present in the B-TFIID complex, which is composed of TBP and TAFII170 (BTAF1) in a 1:1 ratio.^[4] TFIID and B-TFIID are not equivalent, since transcription reactions utilizing TFIID are responsive to gene specific transcription factors such as SP1, while reactions reconstituted with B-TFIID are not.^[4]

Subunits in the TFIID complex include:^[1]

• TBP (TATA binding protein)
• TAF1 (TAFII250)
• TAF2 (CIF150)
• TAF3 (TAFII140)
• TAF4 (TAFII130/135)
• TAF4B (TAFII105)
• TAF5 (TAFII100)
• TAF6 (TAFII70/80)
• TAF7 (TAFII55)
• TAF8 (TAFII43)
• TAF9 (TAFII31/32)
• TAF9B (TAFII31L)
• TAF10 (TAFII30)
• TAF11 (TAFII28)
• TAF12 (TAFII20/15)
• TAF13 (TAFII18)
• TAF15 (TAFII68)

See also

• Eukaryotic transcription
• General transcription factor
• Preinitiation complex
• Regulation of gene expression
• RNA polymerase II holoenzyme
• TATA Binding Protein
• Transcription (genetics)

References

1. Lee, Tong Ihn; Young, Richard A. (2000). "Transcription of eukaryotic protein-coding genes". Annu. Rev. Genet. 34: 77–137. doi:10.1146/annurev.genet.34.1.77. PMID 11092823.
2. Dynlacht, Brian David; Hoey, Timothy; Tjian, Robert (Aug 1991). "Isolation of co-activators associated with the TATA-binding protein that mediate transcriptional activation". Cell. 66 (3): 563–576. doi:10.1016/0092-8674(81)90019-2. PMID 1907890.
3. "NCBI Entrez GeneID: 9044 BTAF1 BTAF1 RNA polymerase II, B-TFIID transcription factor-associated, 170kDa (Mot1 homolog, S. cerevisiae)".
4. Timmers, H.; Meyers, RE; Sharp, PA (Sep 1992). "Composition of transcription factor B-TFIID" (PDF). Proc Natl Acad Sci USA. 89 (17): 8140–4. doi:10.1073/pnas.89.17.8140. PMC 49872. PMID 1387711.

External links

• Transcription Factor TFIID at the US National Library of Medicine Medical Subject Headings (MeSH)
• 3D electron microscopy structures of TFIID from the EM Data Bank(EMDB)