The TATA-box binding protein (TBP) is required for the initiation of transcription by RNA polymerases I, II and III, from promoters with or without a TATA box [, ]. TBP associates with a host of factors, including the general transcription factors SL1, TFIIA, -B, -D, -E, and -H, to form huge multi-subunit pre-initiation complexes on the core promoter. Through its association with different transcription factors, TBP can initiate transcription from different RNA polymerases. There are several related TBPs, including TBP-like (TBPL) proteins []. TBP binds directly to the TATA box promoter element, where it nucleates polymerase assembly, thus defining the transcription start site.The C-terminal core of TBP (~180 residues) is highly conserved and contains two 77-amino acid repeats that produce a saddle-shaped structure that straddles the DNA; this region binds to the TATA box and interacts with transcription factors and regulatory proteins []. By contrast, the N-terminal region varies in both length and sequence.
The TATA-box binding protein (TBP) is required for the initiation of transcription by RNA polymerases I, II and III, from promoters with or without a TATA box [, ]. The core of TBP (~180 residues) is highly conserved and contains two 77-amino acid repeats that produce a saddle-shaped structure that straddles the DNA; this region binds to the TATA box, and interacts with transcription factors and regulatory proteins []. TBP shares structural similarity with the C-terminal of beta(2)-adaptin, which is one of four subunits that comprise the clathrin adaptor. This structure can also be found in the N terminus of RNase H3. The N terminus of RNase H3 is suggested to be a substrate binding domain [].
Transcription initiation factor IIB stabilises the TBP (TATA-binding protein) binding to an archaeal box-A promoter. It is also responsible for recruiting RNA polymerase II to the pre-initiation complex (DNA-TBP-TFIIB).
The TATA-box binding protein (TBP) is required for the initiation of transcription by RNA polymerases I, II and III, from promoters with or without a TATA box [, ]. TBP associates with a host of factors, including the general transcription factors SL1, TFIIA, -B, -D, -E, and -H, to form huge multi-subunit pre-initiation complexes on the core promoter. Through its association with different transcription factors, TBP can initiate transcription from different RNA polymerases. There are several related TBPs, including TBP-like (TBPL) proteins []. TBP binds directly to the TATA box promoter element, where it nucleates polymerase assembly, thus defining the transcription start site.The C-terminal core of TBP (~180 residues) is highly conserved and contains two 77-amino acid repeats that produce a saddle-shaped structure that straddles the DNA; this region binds to the TATA box and interacts with transcription factors and regulatory proteins []. By contrast, the N-terminal region varies in both length and sequence.This entry refers to TBPs found in eukaryotes.
This entry refers to TBPs found in archaea.The TATA-box binding protein (TBP) is required for the initiation of transcription by RNA polymerases I, II and III, from promoters with or without a TATA box [, ]. TBP associates with a host of factors, including the general transcription factors SL1, TFIIA, -B, -D, -E, and -H, to form huge multi-subunit pre-initiation complexes on the core promoter. Through its association with different transcription factors, TBP can initiate transcription from different RNA polymerases. There are several related TBPs, including TBP-like (TBPL) proteins []. TBP binds directly to the TATA box promoter element, where it nucleates polymerase assembly, thus defining the transcription start site.The C-terminal core of TBP (~180 residues) is highly conserved and contains two 77-amino acid repeats that produce a saddle-shaped structure that straddles the DNA; this region binds to the TATA box and interacts with transcription factors and regulatory proteins []. By contrast, the N-terminal region varies in both length and sequence.
This family of proteins bind to DNA and to TBP (TATA box binding protein), TATA-binding protein (TBP)-related protein 2 (TRF2) and several polycomb factors. It is likely to function as a transcription regulator [, ].
This superfamily represents the C-terminal of the TBP-interacting proteins (TIPs), which includes several newly discovered transcription factors that could interact with TBP (TATA-box binding protein). This interaction would in turn prevent interaction between TBP and TATA-DNA, required for basal transcription in eukaryotic and archaeal cells. The C-terminal domain comprises three α-helices, six β-strands, and two 3(10)-helices; however, the specific function of this domain is yet to be elucidated [].
In eukaryotes, the general transcription factor TFIID helps to regulate transcription by RNA polymerase II from class II promoters. TFIID consists of TATA-box-binding proteins (TBP) and TBP-associated factors (TAFIIs), which together mediate both activation and inhibition of transcription. In Drosophila, the N-terminal region of TAFII-230 (the TFIID 230kDa subunit) binds directly to TBP, thereby inhibiting the binding of TBP to the TATA box. The N-terminal domain is comprised of three alpha helices and a beta hairpin, which forms the core that occupies the DNA-binding surface of TBP [].
In eukaryotes, the general transcription factor TFIID helps to regulate transcription by RNA polymerase II from class II promoters. TFIID consists of TATA-box-binding proteins (TBP) and TBP-associated factors (TAFIIs), which together mediate both activation and inhibition of transcription. In Drosophila, the N-terminal region of TAFII-230 (the TFIID 230kDa subunit) binds directly to TBP, thereby inhibiting the binding of TBP to the TATA box. The N-terminal domain is comprised of three alpha helices and a beta hairpin, which forms the core that occupies the DNA-binding surface of TBP [].
The TATA-binding protein (TBP) is a major target for transcriptional regulation. Mot1, a Swi2/Snf2-related ATPase, dissociates TBP from DNA in an ATP dependent process []. The N-terminal domain of Mot1 has been shown to bind TBP, NC2 and DNA. Its ATPase domain is at the C terminus [].This domain contains the ATP-binding region found in Mot1.
This domain is found in Mot1 and related proteins. The TATA-binding protein (TBP) is a major target for transcriptional regulation. Mot1, a Swi2/Snf2-related ATPase, dissociates TBP from DNA in an ATP dependent process []. The N-terminal domain of Mot1 has been shown to bind TBP, NC2 and DNA. Its ATPase domain is at the C terminus [].
The TATA-binding protein (TBP) is a major target for transcriptional regulation. Mot1, a Swi2/Snf2-related ATPase, dissociates TBP from DNA in an ATP dependent process []. The N-terminal domain of Mot1 has been shown to bind TBP, NC2 and DNA. Its ATPase domain is at the C terminus [].
The SNAPc complex allows the transcription of human small nuclear RNA genes to occur by recognition of the proximal sequence element, the TATA box []. SNAPC2 functions both to specifically recognise the proximal sequence element present in the core promoters of human snRNA genes and to stimulate TBP recognition of the neighbouring TATA box present in human U6 snRNA promoters [, ].
This entry represents subunit A (TATA-binding protein-associated factor TAFI48 or TAF1A) of RNA polymerase I. It is a component of the transcription factor SL1/TIFIB complex involved in the assembly of the pre-initiation complex (PIC). The SL1/TIFIB complex is composed of TBP (TATA-binding protein) and TAF1A (TAFI48), TAF1B (TAFI63) and TAF1C (TAFI110) []. Human ribosomal RNA synthesis by RNA polymerase I requires the activator UBF and the promoter selectivity factor SL1/TIFIB. Both TAF1B/TAFI63 and TAF1C/TAFI110 contact the promoter, whereas TAF1A/TAFI48 serves as a target for interaction with UBF and is required to form a transcriptionally active SL1/TIFIB complex responsive to UBF []. Interaction of the SL1/TIFIB subunits with TBP excluded interaction with the transcription factor IID (TFIID) subunits []. This mutually exclusive binding directs the formation of promoter- and RNA polymerase-selective TBP-TAF complexes. Therefore, TAF1A/TAFI48 may function both as a target to mediate UBF activation and as a class-specific promoter selectivity factor.
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This entry represents the precursor that yields both the alpha and beta subunits of TFIIA. The TFIIA heterotrimer is an essential general transcription initiation factor for the expression of genes transcribed by RNA polymerase II [].
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcriptionpre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This superfamily represents the α-helical domain found at the N-terminal of the gamma subunit of transcription factor TFIIA.
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This superfamily represents the β-barrel domain found at the C-terminal of both TOA1 (or alpha/beta) and TOA2 (or gamma) subunits of TFIIA, and their homologues.
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This entry represents the gamma subunit of transcription factor TFIIA.
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This entry represents the β-barrel domain found at the C-terminal of the gamma subunit of transcription factor TFIIA.
Transcription factor IIA (TFIIA) is one of several factors that form part of a transcription pre-initiation complex along with RNA polymerase II, the TATA-box-binding protein (TBP) and TBP-associated factors, on the TATA-box sequence upstream of the initiation start site. After initiation, some components of the pre-initiation complex (including TFIIA) remain attached and re-initiate a subsequent round of transcription. TFIIA binds to TBP to stabilise TBP binding to the TATA element. TFIIA also inhibits the cytokine HMGB1 (high mobility group 1 protein) binding to TBP [], and can dissociate HMGB1 already bound to TBP/TATA-box.Human and Drosophila TFIIA have three subunits: two large subunits, LN/alpha and LC/beta, derived from the same gene, and a small subunit, S/gamma. Yeast TFIIA has two subunits: a large TOA1 subunit that shows sequence similarity to the N-terminal of LN/alpha and the C-terminal of LC/beta, and a small subunit, TOA2 that is highly homologous with S/gamma. The conserved regions of the large and small subunits of TFIIA combine to form two domains: a four-helix bundle (helical domain) composed of two helices from each of the N-terminal regions of TOA1 and TOA2 in yeast; and a β-barrel (β-barrel domain) composed of β-sheets from the C-terminal regions of TOA1 and TOA2 [].This entry represents the α-helical domain found at the N-terminal of the gamma subunit of transcription factor TFIIA.
Members of this family are part of the SNAPc complex required for the transcription of both RNA polymerase II and III small-nuclear RNA genes. They bind to the proximal sequence element (PSE), a non-TATA-box basal promoter element common to these 2 types of genes.Furthermore, they also recruit TBP and BRF2 to the U6 snRNA TATA box. SNAPc consists of at least four stably associated subunits, SNAP43, SNAP45, SNAP50, and SNAP190. None of the three small subunits can bind to the PSE on their own [].
This region is an all-alpha domain associated with the WD40 helical bundle of the TAF5 subunit of transcription factor TFIID. The domain has distant structural similarity to RNA polymerase II CTD interacting factors. It contains several conserved clefts that are likely to be critical for TFIID complex assembly []. The TAF5 subunit is present twice in the TFIID complex and is critical for the function and assembly of the complex, and the NTD2 (second N-terminal domain) and N-terminal domain are crucial for homodimerisation []. TAF5 has a paralogue gene (TAF5L) which has a redundant function [].The TATA Binding Protein (TBP) Associated Factor 5 (TAF5) is one of several TAFs that bind TBP and are involved in forming Transcription Factor IID (TFIID) complex. TFIID plays an important role in the recognition of promoter DNA and assembly of the preinitiation complex. TFIID complex is composed of the TBP and at least 13 TAFs. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID [].
This family includes the Spt3 yeast transcription factors and the 18kDa subunit from human transcription initiation factor IID, known as TAF13 or TAFII18. Determination of the crystal structure reveals an atypical histone fold [].TBP-associated factor 13 (TAF13) is one of several TAFs that bind TBP and is involved in forming the transcription factor IID (TFIID) complex. TAF13 interacts with TAF11 and makes a histone-like heterodimer similar to H3/H4-like proteins. The dimer may be structurally and functionally similar to the spt3 protein within the SAGA histone acetyltransferase complex [].TFIID is one of seven General Transcription Factors (GTF) (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIID) that are involved in accurate initiation of transcription by RNA polymerase II in eukaryotes. TFIID plays an important role in the recognition of promoter DNA and assembly of the pre-initiation complex. TFIID complex is composed of the TBP and at least 13 TAFs. Each TAF, with the help of a specific activator, is required only for expression of subset of genes and is not universally involved for transcription as are GTFs. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID. Several TAFs interact via histone-fold (HFD) motifs; the HFD is the interaction motif involved in heterodimerization of the core histones and their assembly into nucleosome octamers. The minimal HFD contains three α-helices linked by two loops and are found in core histones, TAFs and many other transcription factors. TFIID has a histone octamer-like substructure.
This region is an all-alpha domain associated with the WD40 helical bundle of the TAF5 subunit of transcription factor TFIID. The domain has distant structural similarity to RNA polymerase II CTD interacting factors. It contains several conserved clefts that are likely to be critical for TFIID complex assembly []. The TAF5 subunit is present twice in the TFIID complex and is critical for the function and assembly of the complex, and the NTD2 (second N-terminal domain) and N-terminal domain are crucial for homodimerisation []. TAF5 has a paralogue gene (TAF5L) which has a redundant function [].The TATA Binding Protein (TBP) Associated Factor 5 (TAF5) is one of several TAFs that bind TBP and are involved in forming Transcription Factor IID (TFIID) complex. TFIID plays an important role in the recognition of promoter DNA and assembly of the preinitiation complex. TFIID complex is composed of the TBP and at least 13 TAFs. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID [].The N-terminal domain of TAF5 has a multihelical structure with a C-terminal beta-alpha(2)-beta motif, one central buried helix and parallel β-ribbon.
TATA-Box binding protein (TBP) is a general factor that plays a central role in the activation of eukaryotic genes transcribed by RNA polymerase II [, ]. TBP binds specifically to the TATA-box promoter element, which lies close to the position of transcription initiation.TBP-like factors (TLF; also called TLP, TRF, TRP) are found in most metazoans. TLFs and TBPs have well-conserved core domains; however, they only share about 60% similarity. TLFs, like TBPs, interact with TFIIA and TFIIB, which arepart of the basal transcription machinery. Yet, in contrast to TBPs, TLFs seem not to interact with the TATA-box and even have a negative effect on the transcription of TATA-containing promoters. Recent results indicate that TLFs are involved in the transcription via TATA-less promoters [, , , , , ].This entry refers to TATA box-binding protein-like proteins.
Transcription factor TFIID (or TATA-binding protein, TBP) []is a generalfactor that plays a major role in the activation of eukaryotic genestranscribed by RNA polymerase II. TFIID binds specifically to the TATA boxpromoter element which lies close to the position of transcription initiation.There is a remarkable degree of sequence conservation of a C-terminal domainof about 180 residues in TFIID from various eukaryotic sources. This region isnecessary and sufficient for TATA box binding. The most significant structuralfeature of this domain is the presence of two conserved repeats of a 77 amino-acid region. The intramolecular symmetry generates a saddle-shaped structurethat sits astride the DNA [].Drosophila TRF (TBP-related factor) []is a sequence-specific transcriptionfactor that also binds to the TATA box and is highly similar to TFIID. Archaebacteria also possess a TBP homologue [].This entry represents a conserved site that spans the last 50 residues of therepeated region.
TFIID is one of several General Transcription Factors (GTFs), which also include TFIIA, TFIIB, TFIIE, TFIIF and TFIIH, that are involved in the accurate initiation of transcription by RNA polymerase II in eukaryotes. TFIID plays an important role in the recognition of promoter DNA and assembly of the pre-initiation complex. Human transcription initiation factor TFIID is composed of the TATA-binding protein (TBP) and at least 13 TBP-associated factors (TAFs) that collectively or individually are involved in activator-dependent transcription [, ].TBP-associated factor 12 (TAF12) is one of several TAFs that bind TBP and are involved in forming the TFIID complex. TAF12 interacts with TAF4 and makes a novel histone-like heterodimer that binds DNA and has a core promoter function of a subset of genes [].This entry represents a domain found in TAF12.
Histones mediate DNA organisation and play a dominant role in regulating eukaryotic transcription. The histone-fold consists of a core of three helices, where the long middle helix is flanked at each end by shorter ones. The histone fold is a structural element that facilitates heterodimerisation [, , ]. Proteins displaying this structure include the nucleosome core histones, which form octomers composed of two copies of each of the four histones, H2A, H2B, H3 and H4; archaeal histone, which possesses only the core domain part of eukaryotic histone; and the TATA-box binding protein (TBP)-associated factors (TAF), where the histone fold is a common motif for mediating TAF-TAF interactions. TAF proteins include TAF(II)18 and TAF(II)28, which form a heterodimer, TAF(II)42 and TAF(II)62, which form a heterotetramer similar to (H3-H4)2, and the negative cofactor 2 (NC2) alpha and beta chains, which form a heterodimer. The TAF proteins are a component of transcription factor IID (TFIID), along with the TBP protein. TFIID forms part of the pre-initiation complex on core promoter elements required for RNA polymerase II-dependent transcription. The TAF subunits of TFIID mediate transcriptional activation of subsets of eukaryotic genes. The NC2 complex mediates the inhibition of TATA-dependent transcription through interactions with TBP.
Transcription initiation factor TFIID is a multimeric protein complex thatplays a central role in mediating promoter responses to various activatorsand repressors. The complex includes TATA binding protein (TBP) and variousTBP-associated factors (TAFS). TFIID is a bona fide RNA polymerase II-specificTATA-binding protein-associated factor (TAF) and is essential for viability []. This entry represents one of the TAFs, TAF10.TFIID acts to nucleate the transcription complex, recruiting the rest ofthe factors through a direct interaction with TFIIB. The TBP subunit of TFIID is sufficient for TATA-element binding and TFIIB interaction, and can support basal transcription. The protein belongs to the TAF2H family.TAF10 is part of other transcription regulatory multiprotein complexes (e.g., SAGA, TBP-free TAF-containing complex [TFTC], STAGA, and PCAF/GCN5). Several TAFs interact via histone-fold motifs. The histone fold (HFD) is the interaction motif involved in heterodimerization of the core histones and their assembly into nucleosome octamer. The minimal HFD contains three α-helices linked by two loops. The HFD is found in core histones, TAFs and many other transcription factors. Five HF-containing TAF pairs have been described in TFIID: TAF6-TAF9, TAF4-TAF12, TAF11-TAF13, TAF8-TAF10 and TAF3-TAF10 [, , ].
The TATA Binding Protein (TBP) Associated Factor 8 (TAF8) is one of several TAFs that bind TBP, and is involved in forming the Transcription Factor IID (TFIID) complex. TAF8 plays a role in the differentiation of preadipocyte fibroblasts to adipocytes; it is also required for the integration of TAF10 into the TAF complex. The mouse ortholog of TAF8 is called taube nuss protein (TBN), and is required for early embryonic development. TBN mutant mice exhibit disturbances in the balance between cell death and cell survival in the early embryo. TAF8 plays a role in the differentiation of preadipocyte fibroblasts to adipocytes; it is also required for the integration of TAF10 into the TAF complex. In yeast and human cells, TAFs have been found as components of other complexes besides TFIID. TAF8 is also a component of a small TAF complex (SMAT), which contains TAF8, TAF10 and SUPT7L. Several TAFs interact via histone-fold motifs. The histone fold (HFD) is the interaction motif involved in heterodimerization of the core histones and their assembly into nucleosome octamer. TAF8 contains an H4 related histone fold motif, and interacts with several subunits of TFIID, including TBP and the histone-fold protein TAF10. Currently, five HF-containing TAF pairs have been described or suggested to exist in TFIID: TAF6-TAF9, TAF4-TAF12, TAF11-TAF13, TAF8-TAF10 and TAF3-TAF10 [, , , , ].This entry represents the C-terminal region of subunit 8 (also known as TAF8) of the transcription factor TFIID []. The adjacent N-terminal region generally contains a histone fold domain (). This subunit is one of the key subunits of TFIID, being one of several general cofactors which are typically involved in gene activation to bring about the communication between gene-specific transcription factors and components of the general transcription machinery [].
The Mediator complex is a coactivator involved in the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator functions as a bridge to convey information from gene-specific regulatory proteins to the basal RNA polymerase II transcription machinery. The Mediator complex, having a compact conformation in its free form, is recruited to promoters by direct interactions with regulatory proteins and serves for the assembly of a functional preinitiation complex with RNA polymerase II and the general transcription factors. On recruitment the Mediator complex unfolds to an extended conformation and partially surrounds RNA polymerase II, specifically interacting with the unphosphorylated form of the C-terminal domain (CTD) of RNA polymerase II. The Mediator complex dissociates from the RNA polymerase II holoenzyme and stays at the promoter when transcriptional elongation begins. The Mediator complex is composed of at least 31 subunits: MED1, MED4, MED6, MED7, MED8, MED9, MED10, MED11, MED12, MED13, MED13L, MED14, MED15, MED16, MED17, MED18, MED19, MED20, MED21, MED22, MED23, MED24, MED25, MED26, MED27, MED29, MED30, MED31, CCNC, CDK8 and CDC2L6/CDK11. The subunits form at least three structurally distinct submodules. The head and the middle modules interact directly with RNA polymerase II, whereas the elongated tail module interacts with gene-specific regulatory proteins. Mediator containing the CDK8 module is less active than Mediator lacking this module in supporting transcriptional activation.The head module contains: MED6, MED8, MED11, SRB4/MED17, SRB5/MED18, ROX3/MED19, SRB2/MED20 and SRB6/MED22. The middle module contains: MED1, MED4, NUT1/MED5, MED7, CSE2/MED9, NUT2/MED10, SRB7/MED21 and SOH1/MED31. CSE2/MED9 interacts directlywith MED4. The tail module contains: MED2, PGD1/MED3, RGR1/MED14, GAL11/MED15 and SIN4/MED16. The CDK8 module contains: MED12, MED13, CCNC and CDK8. Individual preparations of the Mediator complex lacking one or more distinct subunits have been variously termed ARC, CRSP, DRIP, PC2, SMCC and TRAP.Proteins in this entry are subunit Med20 of the Mediator complex, and is found in the non-essential part of the head []. and related to the TATA-binding protein (TBP). TBP is a highly conserved RNA polymerase II general transcription factor that binds to the core promoter and initiates assembly of the pre-initiation complex. Human TRF has been shown to associate with an RNA polymerase II-SRB complex [].
Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [, , , , ]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few []. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target. This entry represents a zinc finger motif found in transcription factor IIB (TFIIB). In eukaryotes the initiation of transcription of protein encoding genes by the polymerase II complexe (Pol II) is modulated by general and specific transcription factors. The general transcription factors operate through common promoters elements (such as the TATA box). At least seven different proteins associate to form the general transcription factors: TFIIA, -IIB, -IID, -IIE, -IIF, -IIG, and -IIH [].TFIIB and TFIID are responsible for promoter recognition and interaction with pol II; together with Pol II, they form a minimal initiation complex capable of transcription under certain conditions. The TATA box of a Pol II promoter is bound in the initiation complex by the TBP subunit of TFIID, which bends the DNA around the C-terminal domain of TFIIB whereas the N-terminal zinc finger of TFIIB interacts with Pol II [, ].The TFIIB zinc finger adopts a zinc ribbon fold characterised by two β-hairpins forming two structurally similar zinc-binding sub-sites []. The zinc finger contacts the rbp1 subunit of Pol II through its dock domain, a conserved region of about 70 amino acids located close to the polymerase active site []. In the Pol II complex this surface is located near the RNA exit groove. Interestingly this sequence is best conserved in the three polymerases that utilise a TFIIB-like general transcription factor (Pol II, Pol III, and archaeal RNA polymerase) but not in Pol I [].
