High impact information on TfIIB

• Control of transcription by Krüppel through interactions with TFIIB and TFIIE beta [1].
• Transcription factor IID, possibly with the cooperation of TFIIA, binds to the TATA element of the promoter, forming a complex that can bind TFIIB (refs 6, 7) followed by RNA polymerase II (refs 6, 8) and other factors [2].
• One or more of these steps is thought to be facilitated by gene-specific transcriptional activation proteins; this seems to require TFIID-associated auxiliary factors and may involve direct contact between the activator and TFIID and/or TFIIB [2].
• Here we show that the activity of the glutamine-rich fushi tarazu activation domain is indeed blocked by truncated TFIIB derivatives in Drosophila Schneider L2 cells, suggesting that it is mediated by interactions with TFIIB [2].
• The carboxyl-terminal two-thirds of TFIIB, which contains two direct repeats and two basic residue repeats, is sufficient for interaction with the TFIID-promoter complex [3].

Biological context of TfIIB

• The TFIIB and TBP genes have several similar features, which include high A + T content (68 to 74%) upstream from the tsp, multiple copies of an ATTATTATT sequence motif in the proximal promoter region, the absence of a consensus TATA-box element, and small introns (55 to 64 nucleotides) [4].
• Structural motifs including the direct repeats, basic repeats, and sigma sequence similarities are well conserved among Drosophila, human, and Xenopus TFIIB [5].
• The coding region of the TFIIB gene is interrupted by three short introns [6].
• The close proximity of the VP16 and TAF40 binding sites on the surface of TFIIB suggests that this region could act as a regulatory interface mediating the effects of activators and coactivators on transcription complex assembly [7].
• This interaction requires the same regions in both molecules necessary for function in vivo and is reduced or eliminated by mutations predicted to disrupt the zinc finger in TFIIB [8].

Other interactions of TfIIB

• To investigate the structure and regulation of the genes encoding components of the basal RNA polymerase II transcriptional machinery, the Drosophila melanogaster genes encoding transcription factor IIB (TFIIB) and the TATA-box-binding protein (TBP) were isolated and characterized [4].
• Excess dTFIIB did not, however, affect the ability of either GAL4-VP16 or Sp1 to stimulate transcription [9].
• By gel mobility-shift analysis, TFIIB, TBP, RAP30, and polymerase were able to assemble into DB and DBPolF30 complexes with transcriptionally competent (wild type or initiator mutant), but not with transcriptionally inactive (TATA and TATA/initiator mutant), versions of the Drosophila Adh promoter [10].
• Well-documented transcription activation mechanisms, such as the recruitment of TFIID and TFIIB, control the early phases of preinitiation complex formation [11].
• We developed an approach called protease footprinting in which the broad-specificity proteases chymotrypsin and alkaline protease were used to probe binding of 32P-end-labeled TFIIB to GAL4-VP16 or TAF40 [7].

Analytical, diagnostic and therapeutic context of TfIIB

• In addition, affinity chromatography indicated a direct binding of the basal factor TFIIB to immobilized dTAFII40 [12].
• Studies examining the mechanism by which transcriptional activators function have suggested that the general transcription factor IIB (TFIIB) can be a target for certain regulatory proteins [8].

References