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Identical components of yeast transcription factor IIIB are required and sufficient for transcription of TATA box-containing and TATA-less genes.

Specific transcription by RNA polymerase III requires recognition of the promoter-bound transcription factor IIIB (TFIIIB), of which the TATA-binding protein (TBP) is a subunit. The recruitment of TFIIIB to TATA-less genes is mediated by protein-protein interactions with transcription factor IIIC (TFIIIC) bound to the box A and box B elements. Here we examine interactions involved in the recruitment of TFIIIB to the TATA element-containing yeast U6 small nuclear RNA gene SNR6. TFIIIC is not required for the formation of TFIIIB-SNR6 gene complexes with purified components. The same three components of TFIIIB that are necessary for TFIIIC-dependent transcription of tRNA genes (recombinant TBP and Brf and the denaturing-gel-purified 90-kDa subunit) are required and sufficient for TATA box-directed U6 transcription. Despite its TFIIIC-independent, DNA sequence-dependent assembly, the TFIIIB-SNR6 complex shares important features with tDNA- and 5S rDNA-TFIIIB complexes, such as extent and location of footprint, stability, and resistance to heparin. These properties are clearly distinct from those of a TBP-SNR6 complex. In the SNR6 gene, box B, the primary binding site for TFIIIC, is suboptimally spaced relative to box A. At limiting TBP concentrations and on bare DNA, TFIIIC stimulates the formation of TFIIIB complexes with SNR6 but contributes poorly, at best, to the formation of properly placed complexes.

Base Sequence↗

The adenovirus E1A repression domain disrupts the interaction between the TATA binding protein and the TATA box in a manner reversible by TFIIB.

The human adenovirus E1A 243 amino acid oncoprotein possesses a transcription repression function that appears to be linked with its ability to induce cell cycle progression and to inhibit cell differentiation. The molecular mechanism of E1A repression has been poorly understood. Recently, we reported that the TATA binding protein (TBP) is a cellular target of E1A repression. Here we demonstrate that the interaction between TBP and the E1A repression domain is direct and specific. The TBP binding domain within E1A 243R maps to E1A N-terminal residues approximately 1 to 35 and is distinct from the TBP binding domain within conserved region 3 unique to the E1A 289R transactivator. An E1A protein fragment consisting of only the E1A N-terminal 80 amino acids (E1A 1-80) and containing the E1A repression function was found to block the interaction between TBP and the TATA box element as shown by gel mobility and DNase protection analysis. Interestingly, a preformed TBP-TATA box promoter complex can be dissociated by E1A 1-80. Further, TFIIB can prevent E1A disruption of TBP-TATA box interaction. TFIIB, like TBP, can overcome E1A repression of transcription in vitro. The ability of the E1A repression domain to block TBP interaction with the TATA box and the ability of TFIIB to reverse E1A disruption of the TBP-TATA box complex implies a mechanism for E1A repression distinct from those of known cellular repressors that target TBP.

Adenovirus E1A Proteins↗

T-box binding site mediates the dorsal activation of myf-5 in Xenopus gastrula embryos.

Myf-5, a member of the muscle regulatory factor family of transcription factors, plays an important role in the determination, development, and differentiation of the skeletal muscle. Factors that regulate the expression of myf-5 itself are not well understood. We show here that a T-box binding site in the Xenopus myf-5 promoter mediated the activation of myf-5 expression through specific interaction with nuclear proteins of gastrula embryos. The T-box binding site could be bound by and respond to T-box proteins. T-box genes could induce Xmyf-5. The results suggest that T-box proteins are involved in the specification of myogenic mesoderm and muscle development.

Animals↗

T-box genes in the ascidian Ciona intestinalis: characterization of cDNAs and spatial expression.

Members of the T-box family of transcription factors share an evolutionarily conserved DNA-binding domain and play significant roles in various processes of embryonic development. Vertebrate T-box genes are categorized into the following five major subfamilies (eight groups), depending on sequence similarities: Brachyury, Tbx1 (Tbx1/10, Tbx15/18/22, Tbx20), Tbx2/3/4/5 (Tbx2/3 and Tbx4/5), Tbx6, and Tbr/Eomes/TBX21. Ascidians are primitive chordates, and their tadpole larva are considered to represent the simplified and basic body plan of vertebrates. In addition, it has been revealed that the ascidian genome contains the basic ancestral complement of genes involved in development. The present characterization of cDNAs and survey of the Ciona intestinalis draft genome demonstrated that the Ciona genome contains a single copy gene for each of the Brachyury, Tbx1/10, Tbx15/18/22, Tbx20, Tbx2/3, and Tbr/Eomes/TBX21 groups, and at least three copies of the Tbx6 subfamily. Each of the Ciona T-box genes shows a characteristic expression pattern, although that of Tbx20 was not determined in the present study. These results provide basic information that will be useful for future studies of the function of each gene, genetic cascades of different T-box genes, and genome-wide surveys of evolutionary changes in the T-box gene structure and organization in this primitive chordate.

Animals↗

T-box genes and heart development: putting the "T" in heart.

Members of the T-box gene family (Tbx) are essential for normal heart development, and mutations in human TBX genes cause congenital cardiovascular malformations. T-box genes have been implicated in early cardiac lineage determination, chamber specification, valvuloseptal development, and diversification of the specialized conduction system in vertebrate embryos. These genes include Tbx1, Tbx2, Tbx3, Tbx5, Tbx18, and Tbx20, all of which exhibit complex temporal spatial regulation in developing cardiac structures. Less is known about T-box genes in invertebrate heart development, but multiple T-box genes are expressed in Drosophila cardiac lineages. The molecular hierarchies and developmental processes controlled by T-box genes in the heart are the focus of this review.

Animals↗

Cooperativity in vivo between the E2 transactivator and the TATA box binding protein depends on core promoter structure.

The E2 transactivator protein of bovine papillomavirus 1 (BPV-1) can strongly stimulate complex promoters such as that of the herpes simplex virus thymidine kinase gene but does not efficiently activate minimal promoters that only contain E2 binding sites and a TATA box. Here we show that overexpression of the human, but not yeast, TATA box binding protein (TBP) in transfection experiments overcomes this block and enables E2 to activate a minimal TATA box-containing promoter. This suggests that recruitment of the TFIID complex to such promoters is normally a rate limiting step for transcriptional activation by E2 in vivo. In contrast, minimal promoters that contain an initiator element in addition to a TATA box are efficiently activated by E2 on its own and this activation is only moderately enhanced by TBP overexpression. In such E2-responsive promoters the TATA box or initiator can be functionally replaced by SP1 binding sites. Both the initiator binding protein, TFII-I, and SP1 have been found to interact physically with components of the TFIID complex. Since either TBP overexpression or the presence of an initiator or SP1 binding sites can increase activation by E2, it seems likely that the principal role of the E2 activation domain is to affect a step in the formation of the transcription initiation complex that occurs after TFIID has bound to the promoter. Sequential action of transcription factors, such as TFII-I, SP1 and E2, may be one type of mechanism underlying the widely observed phenomenon of transcriptional synergy.

Adenoviridae↗

Tbt-1, a new T-box transcription factor induced in activated Th1 and CD8+ T cells.

Differentiation of CD4+ T cells into T helper (Th) 1 or Th2 cells requires the cytokines interleukin (IL)-12 and IL-4, respectively. However, transcription factors that regulate expression of Th1 or Th2 cell-specific genes remain largely unclear. In the present study, a new Th1-specific transcription factor, named Tbt-1 (T-box protein expressed in T lymphocytes), was identified. Tbt-1 is a novel member of the T-box family, which is characterized by a conserved T-box DNA-binding domain. Unlike other known T-box proteins that regulate embryo development and organogenesis, Tbt-1 expression is restricted to adult lymphoid organs. Tbt-1 mRNA is only detected in peripheral lymphoid tissues such as spleen, lymph nodes, and blood leukocytes, but not in thymus or bone marrow. Tbt-1 mRNA is not detected in resting T cells but is strongly induced in differentiating Thl cells and CD8+ cytotoxic effector cells. In contrast, Tbt-1 expression was not observed in the entire process of Th2 cell differentiation. In addition, phylogenetic analyses indicate that Tbt-1 co-evolved with adaptive immune responses. Thus, Tbt-1 is the first T-box transcription factor shown to be specific for Th1 cell differentiation.

Amino Acid Sequence↗

Genome-wide characterization of MADS-box genes and their roles in axillary bud development in tobacco.

A total of 118 NtMADS-box genes were identified in tobacco, revealing their potential roles in axillary bud development. Preliminary overexpression analysis indicated that NtMADS91 promotes axillary bud development. MADS-box transcription factors are core regulators of plant development, but their functions in axillary bud development in Nicotiana tabacum L. have not been systematically elucidated. In this study, 118 NtMADS-box genes were identified from the tobacco genome. Phylogenetic analysis classified them into type I (comprising the Mα and Mγ subfamilies) and type II (comprising the MIKC* and MIKCC clades). Promoter analysis revealed that cis-acting elements were predominantly associated with light and hormone responses. RNA-seq analysis of axillary buds after topping identified 60 differentially expressed NtMADS-box genes, from which 12 candidate genes with significant expression changes were selected. Tissue-specific qRT-PCR revealed that seven of these genes were preferentially expressed in axillary buds, with members of the SOC1 and SVP subfamilies accounting for the majority. Exogenous application of abscisic acid and the strigolactone analog GR24 significantly suppressed the expression of most candidate genes, including NtMADS91. The preliminary overexpression analysis suggested that NtMADS91 may promote axillary bud growth, increasing both the number and length of axillary buds. This study lays a foundation for future dissection of the regulatory mechanisms of the NtMADS-box gene family in axillary bud development and provides promising candidate genes for research related to tobacco axillary bud development.

Nicotiana↗

Analysis of the S-locus structure in Prunus armeniaca L. Identification of S-haplotype specific S-RNase and F-box genes.

The gametophytic self-incompatibility (GSI) system in Rosaceae has been proposed to be controlled by two genes located in the S -locusan S-RNase and a recently described pollen expressed S -haplotype specific F-box gene (SFB). However, in apricot (Prunus armeniaca L.) these genes had not been identified yet. We have sequenced 21 kb in total of the S -locus region in 3 different apricot S -haplotypes. These fragments contain genes homologous to the S-RNase and F-box genes found in other Prunus species, preserving their basic gene structure features and defined amino acid domains. The physical distance between the F-box and the S-RNase genes was determined exactly in the S2-haplotype (2.9 kb) and inferred approximately in the S 1-haplotype (< 49 kb) confirming that these genes are linked. Sequence analysis of the 5' flanking regions indicates the presence of a conserved region upstream of the putative TATA box in the S-RNase gene. The three identified S-RNase alleles (S1, S2 and S4) had a high allelic sequence diversity (75.3 amino acid identity), and the apricot F-box allelic variants (SFB1, SFB2 and SFB4) were also highly haplotype-specific (79.4 amino acid identity). Organ specific-expression was also studied, revealing that S1- and S2-RNases are expressed in style tissues, but not in pollen or leaves. In contrast, SFB1 and SFB2 are only expressed in pollen, but not in styles or leaves. Taken together, these results support these genes as candidates for the pistil and pollen S-determinants of GSI in apricot.

5' Flanking Region↗

Genome-wide analysis of S-Locus F-box-like genes in Arabidopsis thaliana.

The Antirrhinum S-locus F-box gene, AhSLF-S2, has been shown to determine the pollen function of S-RNase-mediated self-incompatibility (SI). Its initial identification led to the discovery of a large family of plant-specific F-box proteins, named the SLF (S-Locus F-box) family, including members from species with or without S-RNase SI system. To investigate the evolution and function of its family members in Arabidopsis, we first identified 92 Arabidopsis F-box proteins related to AhSLF-S2, referred to as AtSFL (S-locus F-box-like) in this report. Phylogenetic analyses with family members from several plant species revealed that they could be classified into five subgroups, and the SLF genes appeared to have had a monophyletic origin. Yeast two-hybrid analyses showed that most AtSFL proteins could interact with one or more ASK (Arabidopsis Skp1-like) proteins, a component of the SCF (Skp1/Cullin or CDC53/F-box) complex, suggesting that AtSFLs may function in the process of ubiquitin/26S proteasome-mediated proteolysis. Transcript analysis found that most of AtSFL genes are expressed ubiquitously and only three of them (AtSFL61, 79 and 85) displayed a tissue-specific pattern. In consistent, phenotypic observations for T-DNA insertion lines of 37 AtSFL genes revealed that most of them are functionally redundant, but inactivation of two AtSFL genes (AtSFL 61 and 70) appears to have caused developmental defects in embryo or female gametophyte. Our results show that a diversified expression and functional pattern are associated with AtSFL genes, indicating that they play important roles in various biological processes in Arabidopsis.

Arabidopsis↗

Control regions of an archaeal gene. A TATA box and an initiator element promote cell-free transcription of the tRNA(Val) gene of Methanococcus vannielii.

To identify the DNA sequences required for initiation of transcription in archaea, the 5'-flanking region of the tRNA(Val) gene of Methanococcus vannielii was modified by deletions, restructuring and site-directed mutagenesis, and the tRNA encoding sequence was replaced by a fortuitous Escherichia coli sequence. The effects of these mutations on promoter function were tested in an homologous cell-free transcription system. The DNA region from position -35 to +9 relative to the transcription start site was sufficient for maximal initiation of cell-free transcription. Removal of the DNA region between -35 and -30 reduced initiation by a factor of 2. Deletions extending to position -24 almost completely abolished specific transcription. Analysis of 16 site-specific mutations in the region from -33 to +2 provided evidence that a conserved A + T-rich sequence (TATA box), centered at -25, is essential for initiation of transcription. Single point mutations in six positions of the TATA box reduced initiation of transcription from 0.2 to 0.01 of wild-type levels. A second conserved motif at the transcription start site (consensus ATGC) could be replaced by some sequences containing a pyrimidine-purine dinucleotide but appeared necessary for a maximal rate of gene transcription. Mutations altering the spacing between the two conserved elements demonstrated that initiation occurs at a strictly defined distance of 22 to 27 base-pairs downstream from the TATA box. Our results support the conclusion that the TATA box is the major DNA region mediating promoter recognition, influencing the efficiency of transcription and specifying the site of transcription initiation. This Methanococcus promoter element closely resembles in structure and function the TATA box of promoters of eukaryotic protein-encoding genes transcribed by RNA polymerase II.

Base Sequence↗

Interaction of upstream stimulatory factor proteins with an E-box located within the human CYP1A2 5'-flanking gene contributes to basal transcriptional gene activation.

Cytochrome P450 (CYP)1A2 is abundantly expressed in the liver of all vertebrate species. In most, its expression is restricted to the liver. Sequence analysis of the human CYP1A2 5'-flanking region from +3 to -3201 identified six E-box motifs within the 3-methylcholanthrene (MC) enhancer element (-1987 to -3201). The E-box motif is recognized by members of the basic helix-loop-helix (bHLH) family of transcription factors. Gel mobility shift and antibody supershift assays were used to examine each of the six upstream E-box motifs for their ability to bind nuclear proteins and to compete with the ubiquitously expressed bHLH protein, upstream stimulatory factor (USF), for binding. We found that USF-1 and USF-2 proteins bind to the upstream E-box motifs EB2, EB3, and EB4. Transient transfection assays in HepG2 cells were performed with different segments of the human CYP1A2 5'-flanking region linked to a luciferase reporter gene. Site-directed mutagenesis of one of the E-box motifs, EB2, resulted in a 60% reduction in basal reporter gene activity. Mutations in EB3 and EB4 had no effect. We found that transfection of expression vectors containing USF-1 or USF-2 cDNAs activated CYP1A2 reporter gene activity, while a dominant-negative USF-2 expression vector blocked such activity. Chromatin immunoprecipitation assays confirmed that the interaction of USF proteins with the CYP1A2 EB2 site occurs in vivo. These data support the role of USF as a constitutive transcriptional activator of human CYP1A2.

5' Flanking Region↗

Composite action of three GC/GT boxes in the proximal promoter region is important for gastrin gene transcription.

The proximal region of the human gastrin gene promoter contains three GC/GT boxes at positions -140 to -134 bp, -108 to -102 bp and -67 to -61 bp. In this study we have examined the significance of the three elements, and their role in Sp1 and Sp3 mediated gastrin transcription. In AGS cells, mutation of each of the boxes caused a moderate decrease in promoter activity from 33 to 63%, whereas double or triple mutations reduced activity to 3-12%. In Drosophila cells Sp1 activated the promoter, mainly through the distal GC box. Similarly, co-transfection of heterologous promoter constructs revealed that only the distal GC box increased activation by Sp1. The effect of Sp3 was cell-line dependent, since Sp3 inhibited the gastrin promoter activity in AGS cells and caused a synergistic activation of the Sp1 stimulated gastrin promoter in Drosophila cells. Both effects were dependent on the C-terminal DNA binding domain of Sp3. The results indicates that the combined effect of the GC/GT boxes and the ratio between Sp1 and Sp3 are important for gastrin gene expression.

Adenocarcinoma↗

Coding defect and a TATA box mutation at the bilirubin UDP-glucuronosyltransferase gene cause Crigler-Najjar type I disease.

Mutations at the bilirubin UDP-glucuronosyltransferase (transferase) gene in a severely hyperbilirubinemic Crigler-Najjar (CN) type I individual was compared with that in a moderately hyperbilirubinemic CN II individual. The CN-I (CF) patient in this study sustained a TATA box insertional mutation which was paired with a coding defect at the second allele, unlike all coding defects previously seen in CN-I patients. The sequence of the mutant TATA box, [A(TA)8A], also seen in the CN-II patient, was compared with that at the wild-type box, [A(TA)7A]. Transcriptional activity with [A(TA)8A] was 10-15% that with the wild-type box when present in the -1.7 kb upstream regulatory region (URR) of the bilirubin transferase UGT1A1 gene which was fused to the chloramphenicol acetyl transferase reporter gene, pCAT 1.7H, and transfected into HepG2 cells. Also, a construct with a TA deletion, [A(TA)6A], was prepared and used as a control; transcriptional activity was 65% normal. The coding region defect, R336W, seen in CF (CN-I) was placed in the bilirubin transferase UGT1A1 [HUG-Br1] cDNA, and its corresponding protein was designated UGT1A1*32. The UGT1A1*32 protein supported 0-10% normal bilirubin glucuronidation when expressed in COS-1 cells. The I294T coding defect seen at the second allele in SM (CN-II) generated the UGT1A1*33 mutant protein which supported 40-55% normal activity with a normal Km (2.5 microM) for bilirubin. The hyperbilirubinemia seen in SM decreased in response to phenobarbital treatment, unlike that seen in CF. Parents of the patients were carriers of the respective mutations uncovered in the offspring. The TATA box mutation paired with a deleterious missense mutation is, therefore, completely repressive in the CN-I patient, and is responsible for a lethal genotype/phenotype; but when homozygous, i.e. paired with itself, as previously reported in the literature, it is far less repressive and generates the mild Gilbert's phenotype.

Bilirubin↗

Characterization of a maize G-box binding factor that is induced by hypoxia.

G-box cis-acting DNA sequence elements are present in the promoter region of a number of signal-inducible plant genes. In many cases this motif is essential for gene expression. Maize nuclear extracts contain a protein complex that binds specifically to the G-box sequence. Previously, a protein called GF14 was described that is physically associated with the G-box binding complex, but is not a DNA-binding factor in and of itself. This paper reports the isolation of a cDNA encoding a maize G-box binding factor (GBF). The deduced amino acid sequence indicates that maize GBF1 is a basic region-leucine zipper protein. GBF1 binds to the G-box element with specificity similar to that of the binding activity in nuclear extracts. Furthermore, maize GBF1 and the factor detected in nuclear extract are identical in their molecular weight and are immunologically related. GBF1 mRNA accumulates rapidly in hypoxically induced maize cells prior to the increase in Adh1 mRNA levels. Taken together with results that indicate that GBF1 binds to the hypoxia-responsive promoter of maize Adh1, these observations suggest that GBF1 may be one of the factors involved in the activation of Adh1.

Alcohol Dehydrogenase↗

Boxing and running lead to a rise in serum levels of S-100B protein.

Permanent neurological dysfunction is the primary medical concern of boxing. Recently it was reported that patients presenting elevated levels of the glial protein S-100B in serum after minor head injuries are more prone to develop neuropsychological deficits than patients with lower levels of S-100B protein. We assessed this protein before and after amateur boxing competitions (n = 10) and sparring bouts (n = 15). In several control groups, we investigated S-100B levels of participants before and after a 25 km race (n = 11), jogging (10 km, n = 12), short-term running (n = 12), and heading footballs (n = 12). There was an increase in S-100B protein after boxing and the running disciplines but not after ergometer cycling or soft heading of footballs. The increase in S-100B protein concentrations due to competitive boxing and after the 25 km race was significantly higher than that after performing other disciplines (p < 0.001). There was no significant difference between the increases caused by sparring and the running disciplines (p = 0.21). The number and severity of the strikes to the head correlated significantly with the increase in the S-100B protein levels. Levels of S-100B protein known to be associated with neuropsychological deficits were not reached in our study. In professional boxing, much higher levels are to be expected and would be worthy of investigation.

Adolescent↗

Direct involvement of the Y-box binding protein YB-1 in genotoxic stress-induced activation of the human multidrug resistance 1 gene.

The human multidrug resistance 1 (MDR1) gene encoding P-glycoprotein is often overexpressed in various human tumors after chemotherapy. During treatment with various chemotherapeutic agents, the MDR1 gene is activated at the transcriptional level and/or amplified, resulting in overexpression. Our previous studies demonstrated that an inverted CCAAT box (Y-box) might be a critical cis-regulatory element regulating UV or drug-induced MDR1 gene expression. We have now established various cell lines from human head and neck cancer KB cells which were stably transfected with the chloramphenicol acetyltransferase (CAT) reporter gene driven by various MDR1 promoter deletion constructs. Transient transfection of antisense YB-1 expression constructs resulted in a decrease of both YB-1 protein levels and DNA binding activity to the inverted CCAAT box, as determined by Western blot and gel mobility shift assays. The limited expression and binding activity due to expression of antisense YB-1 constructs were also observed when cells were treated with UV. CAT activity of constructs containing the Y-box was enhanced after treatment with UV irradiation as well as genotoxic agents such as cisplatin and etoposide. Moreover, this activation was reduced by 50-80% by transfection of antisense YB-1 expression constructs. In contrast, transfection of antisense YB-1 expression constructs had no effect on CAT activity driven by MDR1 promoter constructs not containing the Y-box. These data indicate that YB-1 is directly involved in MDR1 gene activation in response to genotoxic stress.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

The upstream region of the Rpe65 gene confers retinal pigment epithelium-specific expression in vivo and in vitro and contains critical octamer and E-box binding sites.

RPE65 is essential for all-trans- to 11-cis-retinoid isomerization, the hallmark reaction of the retinal pigment epithelium (RPE). Here, we identify regulatory elements in the Rpe65 gene and demonstrate their functional relevance to Rpe65 gene expression. We show that the 5' flanking region of the mouse Rpe65 gene, like the human gene, lacks a canonical TATA box and consensus GC and CAAT boxes. The mouse and human genes do share several cis-acting elements, including an octamer, a nuclear factor one (NFI) site, and two E-box sites, suggesting a conserved mode of regulation. A mouse Rpe65 promoter/beta-galactosidase transgene containing bases -655 to +52 (TR4) of the mouse 5' flanking region was sufficient to direct high RPE-specific expression in transgenic mice, whereas shorter fragments (-297 to +52 or -188 to +52) generated only background activity. Furthermore, transient transfection of analogous TR4/luciferase constructs also directed high reporter activity in the human RPE cell line D407 but weak activity in the non-RPE cell lines HeLa, HepG2, and HS27. Functional binding of potential transcription factors to the octamer sequence, AP-4, and NFI sites was demonstrated by directed mutagenesis, electrophoretic mobility shift assay, and cross-linking. Mutations of these sites abolished binding and corresponding transcriptional activity and indicated that octamer and E-box transcription factors synergistically regulate the RPE65 promoter function. Thus, we have identified the regulatory region in the Rpe65 gene that accounts for tissue-specific expression in the RPE and found that octamer and E-box transcription factors play a critical role in the transcriptional regulation of the Rpe65 gene.

5' Untranslated Regions↗