Showing papers on "Transcription factor published in 1987"
TL;DR: Results strongly suggest that AP-1 is at the receiving end of a complex pathway responsible for transmitting the effects of phorbol ester tumor promoters from the plasma membrane to the transcriptional machinery.
2,773 citations
TL;DR: Activation of T cells, which increases HIV expression up to 50-fold, correlated with induction of a DNA binding protein indistinguishable from a recognized transcription factor, called NF-κB, with binding sites in the viral enhancer.
Abstract: Human immunodeficiency virus (HIV) production from latently infected T lymphocytes can be induced with compounds that activate the cells to secrete lymphokines. The elements in the HIV genome which control activation are not known but expression might be regulated through a variety of DNA elements. The cis-acting control elements of the viral genome are enhancer and promoter regions. The virus also encodes trans-acting factors specified by the tat-III and art genes. We have examined whether products specific to activated T cells might stimulate viral transcription by binding to regions on viral DNA. Activation of T cells, which increases HIV expression up to 50-fold, correlated with induction of a DNA binding protein indistinguishable from a recognized transcription factor, called NF-kappa B, with binding sites in the viral enhancer. Mutation of these binding sites abolished inducibility. That NF-kappa B acts in synergy with the viral tat-III gene product to enhance HIV expression in T cells may have implications for the pathogenesis of AIDS (acquired immune deficiency syndrome).
1,970 citations
TL;DR: It is demonstrated that multiple synthetic copies of the consensus AP-1-binding site can act as TPA-inducible enhancers in various plasmid constructs after transfection into HeLa cells, suggesting that AP- 1 is a transcription factor that functions by interacting with a specific enhancer element, and that its activities may be modulated by treatment of cells with TPA.
1,877 citations
TL;DR: Together the hMR and hGR provide unexpected functional diversity in which hormone-binding properties, target gene interactions, and patterns of tissue-specific expression may be used in a combinatorial fashion to achieve complex physiologic control.
Abstract: Low-stringency hybridization with human glucocorticoid receptor (hGR) complementary DNA was used to isolate a new gene encoding a predicted 107-kilodalton polypeptide. Expression studies demonstrate its ability to bind aldosterone with high affinity and to activate gene transcription in response to aldosterone, thus establishing its identity as the human mineralocorticoid receptor (hMR). This molecule also shows high affinity for glucocorticoids and stimulates a glucocorticoid-responsive promoter. Together the hMR and hGR provide unexpected functional diversity in which hormone-binding properties, target gene interactions, and patterns of tissue-specific expression may be used in a combinatorial fashion to achieve complex physiologic control.
1,854 citations
TL;DR: The 50 kd activator protein 2 (AP-2) as discussed by the authors is another enhancer-binding protein interacting with the human metallothionein IIA (hMT-IIA) gene control region.
1,248 citations
TL;DR: Deletion analysis of promoter-linked transfection assays and competition of these constructions in cells with a synthetic FSE2 element suggest that trans-acting factors bind to this region and act as negative regulators of aP2 gene activity in preadipocytes.
465 citations
TL;DR: The yeast heat-shock factor binds constitutively to DNA but only activates transcription after heat-induced phosphorylation, and the mobility of protein-HSE complexes on polyacrylamide gels is altered following heat shock.
Abstract: When cells are exposed to elevated temperatures, transcription of a small set of genes, the heat-shock genes, is activated. This response is mediated by a short DNA sequence, the heat-shock element (HSE), which is thought to be the binding site for a specific transcription factor. Studies with Drosophila show that this protein binds to HSEs only in heat-shocked cells, suggesting that changes in factor binding are responsible for gene activation. We have investigated the properties of HSE-binding proteins from yeast and HeLa cells. In HeLa cells, binding activity is present only after heat shock. In contrast, control and heat-shocked yeast cells yield the same amount of HSE-binding activity; however, the mobility of protein-HSE complexes on polyacrylamide gels is altered following heat shock. This mobility difference can be significantly reduced by treatment of crude extracts with phosphatase. We propose that the yeast heat-shock factor binds constitutively to DNA but only activates transcription after heat-induced phosphorylation.
429 citations
TL;DR: The promoter of the mouse albumin gene contains at least six binding sites for specific DNA-binding proteins (A to F), and both of these competing binding sites are required for maximal in vitro transcription.
423 citations
TL;DR: An octamer-binding transcription factor, OTF-1, which stimulates transcription of a human histone H2b gene, has been purified from HeLa nuclear extracts through the use of DNA affinity chromatography, and the factor retained the ability to efficiently stimulate H 2b transcription in a reconstituted in vitro system.
418 citations
TL;DR: It is shown that point mutations replacing two cysteines by two histidines in the first potential DNA-binding finger of the human oestrogen receptor (hER) prevent it from activating gene transcription, and region C determines the receptor's specificity for target genes.
Abstract: Steroid hormone receptors are a class of cell-specific trans-acting transcription regulatory factors whose activity is controlled by specific binding of the hormone. The hormone-receptor complex appears to associate with promoter/enhancer elements of specific target genes, resulting in activation of transcription (see refs 1 and 2 for reviews). Sequence comparison between the oestrogen, glucocorticoid and progesterone receptors (refs 7, 8 and unpublished results) and site-directed mutation analysis, has identified in each at least two functional domains important for steroid receptor function. Region E (Fig. 1a), is the hormone-binding domain; region C is a 66-amino-acid region (Figs 1a,b) that is more highly conserved than the hormone-binding domain and has the potential to form at least two zinc-stabilized 'DNA-binding fingers' analogous to those proposed for the Xenopus transcription factor TFIIIA. We and others have suggested that this region may be the receptor's DNA-binding domain. We show here that point mutations replacing two cysteines by two histidines in the first potential DNA-binding finger of the human oestrogen receptor (hER) prevent it from activating gene transcription. We further show that a chimaeric receptor formed by replacing this 66-amino-acid region of the hER with that of the human glucocorticoid receptor (hGR) activates expression of a glucocorticoid-inducible gene, but not of an oestrogen-inducible gene, in the presence of oestradiol. Thus, region C determines the receptor's specificity for target genes.
413 citations
TL;DR: The results demonstrate that glucocorticoid induction of transcription results from receptor-mediated establishment of a transcription factor complex at the promoter rather than activation of a preexisting complex.
TL;DR: A short DNA sequence element, the serum response element (SRE), which binds a nuclear protein, serum response factor (SRF), mediates transient transcriptional activation of c‐fos and cytoskeletal actin genes in response to serum factors.
Abstract: A short DNA sequence element, the serum response element (SRE), which binds a nuclear protein, serum response factor (SRF), mediates transient transcriptional activation of c-fos and cytoskeletal actin genes in response to serum factors. Variant SRE sequences with different affinities for HeLa cell SRF were synthesised. Binding of SRF to these sites in vitro correlates with the transcriptional properties of these elements in vivo, suggesting that SRF is a positively acting transcription factor. A 67-kd polypeptide was identified as the DNA-binding component of SRF by photoactivated DNA-protein cross-linking in vitro. The high affinity SRF-binding site was used to purify this polypeptide to virtual homogeneity in a single DNA affinity chromatography step.
TL;DR: It is shown that within 30 seconds of heat shock of intact cells the sequence-specific binding activity in whole cell extracts increases significantly, reaching a plateau by 5min after the start of the shock; removal of the heat stimulus returns the activity to basal levels.
Abstract: Drosophila tissue culture cells stimulated by heat shock contain high levels of heat shock activator protein, which binds specifically to the heat-shock control DNA element. In contrast, nonshocked cells have low basal levels of binding activity. Here, we show that within 30 seconds of heat shock of intact cells the sequence-specific binding activity in whole cell extracts increases significantly, reaching a plateau by 5 min after the start of the shock; removal of the heat stimulus returns the activity to basal levels. Known chemical inducers of heat-shock genes elicit a similar pattern of specific binding activity. Moreover, this pattern is observed in the presence of protein synthesis inhibitors, even if the stimulus-withdrawal is repeated sequentially through five cycles. Our results are inconsistent with models which propose proteolysis as the chief means of mediating heat-shock transcriptional control. Rather, they suggest that heat shock activator pre-exists in normal cells in a nonbinding form, which is converted upon cell stimulus to a high affinity, sequence-specific binding form, most probably by a post-translational modification. This conversion may be crucial for the transcriptional activation of heat shock genes.
TL;DR: The relative affinities of the protein for a range of variant HSE sequences correlates with the ability of these sequences to support heat‐inducible transcription in vivo, suggesting that this polypeptide is involved in the activation of heat‐shock promoters.
Abstract: The promoters of heat shock genes are activated when cells are stressed. Activation is dependent on a specific DNA sequence, the heat-shock element (HSE). We describe the purification to homogeneity of an HSE-binding protein from yeast (Saccharomyces cerevisiae), using sequential chromatography of whole cell extracts on heparin-agarose, calf thymus DNA-Sepharose and an affinity column consisting of a repetitive synthetic HSE sequence coupled to Sepharose. The protein runs as a closely spaced doublet of approximately 150 kd on SDS-polyacrylamide gels; mild proteolysis generates a stable 70-kd fragment which retains DNA binding activity. The relative affinities of the protein for a range of variant HSE sequences correlates with the ability of these sequences to support heat-inducible transcription in vivo, suggesting that this polypeptide is involved in the activation of heat-shock promoters. However, the protein was purified from unshocked yeast, and may therefore represent an unactivated form of heat-shock transcription factor. Study of the purified protein should help to define the mechanistic basis of the heat-shock response.
TL;DR: This B cell-specific octamer-binding factor, in pure form, activated transcription from a kappa light chain promoter in vitro, thus demonstrating that it is indeed a Bcell-specific transcription factor for this gene.
TL;DR: It is suggested that binding of several molecules of E2 protein between the viral CAAT and TATA elements sterically hinders transcription initiation from this promoter, while the same DNA–protein assembly stimulates the SV40 promoter when cloned in an enhancer configuration upstream of this heterologous promoter.
Abstract: The human papillomavirus 18 (HPV 18) long control region contains promoter and enhancer elements whose activity is restricted to several human cell lines of epithelial origin. This enhancer possesses a considerable constitutive activity which is further stimulated in the presence of the E2 trans-activating protein of bovine papillomavirus 1 (BPV1). Surprisingly the same BPV1 protein strongly repressed transcription from the genuine HPV18 enhancer-promoter DNA sequences. We suggest that binding of several molecules of E2 protein between the viral CAAT and TATA elements sterically hinders transcription initiation from this promoter, while the same DNA--protein assembly stimulates the SV40 promoter when cloned in an enhancer configuration upstream of this heterologous promoter. Unlike BPV1-E2 the homologous E2 gene product does not seem to strongly modulate viral transcription. Finally the BPV1-E2 gene product may repress some essential viral or host genes, since we failed to isolate HeLa cells expressing BPV1-E2.
TL;DR: The design of an artificial protein bearing a novel 15-amino acid peptide linked to a DNA binding fragment of the yeast regulatory protein GAL4 is reported, which efficiently activates the GAL1 gene which is ordinarily activated by GAL 4.
Abstract: Gene activation by a DNA-binding regulatory protein in yeast requires the protein to have two components: one to recognize a specific DNA sequence and a second, the 'activating region', to interact with a general transcription factor or perhaps with RNA polymerase1,2. The activating regions that have been characterized are acidic3,4, and mutational analysis of one indicates that this acidity is important for activity6. Here we report the design of an artificial protein bearing a novel 15-amino acid peptide linked to a DNA binding fragment of the yeast regulatory protein GAL4 (refs 7–10). The synthetic peptide is acidic and should it form an α-helix, that helix would be amphipathic, having one hydrophilic face bearing the acidic residues, and one hydrophobic face11. When expressed in yeast, the artificial protein bearing this peptide efficiently activates the GAL1 gene which is ordinarily activated by GAL4 (refs 12, 13). An otherwise identical protein with the novel 15 amino acids in a scrambled order, and which is thus unable to form an amphipathic structure, does not activate GAL1 transcription.
TL;DR: In this article, the authors performed DNase I footprinting of the viral LTR using partially purified HeLa cell extracts and found that the negative regulatory, enhancer, SP1, TATA and untranslated regions are critical for DNA binding of cellular proteins.
Abstract: The human immunodeficiency virus (HIV) is a human retrovirus which is the etiologic agent of the acquired immunodeficiency syndrome. To study the cellular factors involved in the transcriptional regulation of this virus, we performed DNase I footprinting of the viral LTR using partially purified HeLa cell extracts. Five regions of the viral LTR appear critical for DNA binding of cellular proteins. These include the negative regulatory, enhancer, SP1, TATA and untranslated regions. Deletion mutagenesis of these binding domains has significant effects on the basal level of transcription and the ability to be induced by the viral tat protein. Mutations of either the negative regulatory or untranslated regions affect factor binding to the enhancer region. In addition, oligonucleotides complementary to several of the binding domains specifically compete for factor binding. These results suggest that interactions between several distinct cellular proteins are required for HIV transcriptional regulation.
TL;DR: The growth hormone (GH) gene is specifically expressed in the anterior pituitary and the tissue specificity of the hGH promoter appears to be positively controlled by the abundance or activity of GHF-1, a positively acting, cell-type- and promoter-specific transcription factor.
TL;DR: It is concluded that E2F is likely to be responsible for the E1A-mediated stimulation of the E 1A gene as well as the E2 gene but is not involved in the activation of the other E1a-inducible promoters.
Abstract: A product of the adenovirus gene E1A is responsible for the stimulation of transcription from six viral promoters as well as at least two cellular promoters. We have detected a HeLa cell factor, termed E2 promoter binding factor (E2F), that appears to mediate the transcriptional stimulation of the viral E2 promoter. Competition experiments revealed that E2F did not recognize and bind to the E1B, E3, E4, or major late promoter sequences. Furthermore, three additional promoters stimulated by E1A, heat shock protein 70, beta-globin, and early simian virus 40, do not bind E2F. In contrast, the factor does recognize sequences in the E1A enhancer, and within the E1A enhancer are duplicated binding sites for E2F. Finally, a single E2F binding site from the E1A enhancer can confer increased transcription to a mouse beta-globin promoter, dependent on the action of the E1A gene product. This stimulation requires binding of E2F since methylation of the binding site, which blocks binding in vitro, reduces transcription stimulation in vivo. We, therefore, conclude that E2F is likely to be responsible for the E1A-mediated stimulation of the E1A gene as well as the E2 gene but is not involved in the activation of the other E1A-inducible promoters.
TL;DR: It is demonstrated here that E4F1 and E2A-EF have identical DNA-binding specificity, which indicates a significant role for ATF in E1A-mediated transcriptional activation.
Abstract: We have examined the relationship between sequence-specific DNA-binding proteins that activate transcription of E1A-inducible adenovirus early promoters. Factors previously referred to as E4F1 and E2A-EF bind to the E4 and E2A promoters, respectively. We demonstrate here that E4F1 and E2A-EF have identical DNA-binding specificity. Moreover, E4F1 and E2A-EF both activate transcription of the E4 and E2A promoters in vitro. These findings demonstrate that E4F1 and E2A-EF are the same factor, which we have designated activating transcription factor, or ATF. In addition to the E4 and E2A promoters, ATF binds to an important functional element of the E1A-inducible E3 promoter. Interaction of a common activator protein, ATF, with multiple E1A-inducible early viral promoters, suggests a significant role for ATF in E1A-mediated transcriptional activation.
TL;DR: Using synthetic oligonucleotides, a systematic series of block replacement mutants spanning this region is constructed and simultaneous mutation of two of the most mutationally sensitive regions leads to virtual abolition of activity.
Abstract: Cell-specific expression of the insulin gene is controlled by cis-acting DNA sequences located within approximately equal to 350 base pairs of the 5' flanking DNA immediately upstream from the transcription start site. Using synthetic oligonucleotides, we have constructed a systematic series of block replacement mutants spanning this region. No single sequence appears to be absolutely required for expression. However, three of the mutants exhibit 5-10 times less activity and several others show 2-3 times less. Simultaneous mutation of two of the most mutationally sensitive regions leads to virtual abolition of activity. These two elements are structurally related and presumably represent key components of the machinery determining the cell-specific expression of the insulin gene.
TL;DR: Tissue specificity of the hGH promoter seems to be determined by the binding of at least one tissue‐specific trans‐acting factor, acting in concert with several other more ubiquitous, yet specific, DNA binding proteins.
Abstract: The molecular basis for the pituitary-specific expression of the human growth hormone (hGH) gene was investigated, by gene transfer and protein footprinting experiments. Plasmid constructs in which CAT or Neo transcription units are fused to a 0.5 kb fragment of the hGH 5' sequences were efficiently expressed in GC and GH3 cells, derived from a pituitary tumor, but not in cell lines of other origins, indicating the presence of a tissue-specific promoter. DNaseI footprinting experiments have identified at least three factors that specifically bind to the hGH 5' region. While two of these factors were also detected in extracts of non-expressing cells, the third factor, GHF-1, was detected only in extracts of GH expressing pituitary tumor cells. Mutagenesis experiments suggest that binding of GHF-1 and some of the other more ubiquitous factors is required for optimal hGH promoter activity in vivo. Tissue specificity of the hGH promoter therefore seems to be determined by the binding of at least one tissue-specific trans-acting factor, acting in concert with several other more ubiquitous, yet specific, DNA binding proteins.
TL;DR: Results indicate that the jun oncoprotein binds the same DNA sequences as GCN4, and strongly suggest that jun is derived from a normal cellular transcription factor (possibly AP-1, which recognizes similar sequences).
TL;DR: Transfection data plus DNAase I footprinting experiments suggest a model of end-product repression in which the end product (sterols) opposes the action of a positive transcription factor that binds to a discrete promoter element.
TL;DR: In the 5'-flanking region of the heme oxygenase gene, several potential binding sites for different transcription factors are found: a transcription factor Sp1, a positive regulator for the control of amino acid synthesis (GCN4), a heat shock transcription factor, and a metal-dependent transcription factor.
TL;DR: A detailed mutational analysis of the adenovirus E1B promoter was undertaken to define the DNA sequences required for proper basal transcription and E1A transactivation, and two key findings emerged: first the E 1B promoter is an unusually simple RNA polymerase II promoter requiring only two sequence elements for proper regulation, the TATA box2 and a binding site for transcription factor Sp13,4.
Abstract: Adenovirus E1A proteins stimulate transcription by RNA polymerases II and III from many promoters. The detailed mechanism of transcriptional activation (transactivation) by E1A proteins remains unclear, but genetic and biochemical results suggest that E1A products might act to stimulate the activity of cellular transcription factors. In this study, a detailed mutational analysis of the adenovirus E1B promoter was undertaken to define the DNA sequences required for proper basal transcription and E1A transactivation. Two key findings emerged: first the E1B promoter is an unusually simple RNA polymerase II promoter requiring only two sequence elements for proper regulation, the TATA box and a binding site for transcription factor Sp1; and second only mutations in the TATA box interfere with E1A-transactivation, suggesting that E1A mediates its effect on this promoter through the TATA-box transcription factor.
TL;DR: The hybrid gene approach, so successful for PEPCK and HMG-CoA reductase, also will be effective in defining cis-acting hormone- or metabolite-regulatory elements in other genes, and should be applicable to both transcriptional and post-transcriptional mechanisms.
Abstract: The mechanisms of the responses of an enzyme to different hormones and metabolites or several enzymes to a single hormone are surprisingly varied. There is neither an operon for lipogenic enzymes nor a common step at which hormones and metabolites coordinately regulate the expression of lipogenic genes. In bacteria, coordinated expression of several enzymes in a single metabolic pathway often is achieved by organizing the genes into operons. An operon is a group of genes linked together in a linear fashion and producing a polycistronic mRNA. Trans-acting factors regulate the transcription of these genes by interacting with promoter/regulatory sequences in the 5'-flanking region of the most 5'-ward of the genes. In vertebrate animals, however, coordinated control of gene transcription is not achieved by linking the individual genes, but by putting in the 5'-flanking regions of these genes a regulatory sequence that interacts with common trans-acting factors. Genes controlled by different hormones are expected to have regulatory elements for each hormone. The presence of glucocorticoid and cyclic AMP regulatory elements at the 5'-end of the PEPCK gene is consistent with this notion. Transcription is not the only step at which hormones and metabolites control the pathways for gene expression. The levels of the mRNAs for L-PK, ME, S11, and S14 are increased by T3 at post-transcriptional steps. Glucagon also regulates the accumulation of ME mRNA post-transcriptionally. Neither the mechanism nor the sequence organization of regulatory elements is known for post-transcriptional control of gene expression. In the case of PEPCK and HMG-CoA reductase, the next steps will be to determine more precisely the sequences in the 5'-region that mediate hormone sensitivity and feedback inhibition, respectively, and whether trans-acting factors are involved. For the other genes discussed, identification of the regulated step must precede identification of sequences that confer hormone or metabolite-sensitive regulation on a specific gene. In general, it is probable that the hybrid gene approach, so successful for PEPCK and HMG-CoA reductase, also will be effective in defining cis-acting hormone- or metabolite-regulatory elements in other genes. These techniques should be applicable to both transcriptional and post-transcriptional mechanisms. Our long-term objective is to understand the molecular basis of each event that intervenes between the binding of hormone or metabolite to its appropriate receptor and altered enzyme level.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: This article summarizes what is known about transcriptional controls of mating and mating-type switching in homothallic yeast and discusses possible parallels in higher eukaryotes.
Abstract: The transition from haploid to diploid in homothallic yeast involves a defined sequence of events which are regulated at the level of transcription. Transcription factors encoded by SWI genes activate the HO endonuclease gene at a precise stage in the cell cycle of mother cells. The HO endonuclease initiates a transposition event which activates genes of the opposite mating type by causing them to move away from a silencer element. The activated mating type genes then regulate genes involved in cell signaling such as the mating type-specific pheromones and their receptors. Since HO is only activated in one of the sister cells after division (the mother), adjacent cells of opposite mating type are generated which respond to each others' secreted pheromones by inducing genes involved in conjugation. This leads to the formation of a diploid in which many of the genes involved in mating and mating-type switching become repressed due to the heterozygosity of the mating-type locus. This article summarizes what is known about these transcriptional controls and discusses possible parallels in higher eukaryotes.
TL;DR: Results suggest that the E4 promoter may be comprised solely of multiple E4F1 binding sites and a TATA box and thus may be involved in the co‐ordinate expression of E1a‐inducible early viral genes.
Abstract: Efficient transcription of the adenovirus E1a-inducible E4 gene is mediated by an E1a-dependent enhancer in vivo. In vitro, the enhancer functions constitutively in the absence of E1a, conferring high levels of transcription on the E4 and heterologous promoters. Binding of a cellular transcription factor, E4F1, to two sites within the E4 enhancer and to one other functionally important site located directly upstream of the E4 TATA box is required for transcriptional activity. The relationship between the enhancer and the TATA box proximal site is further demonstrated by the fact that the E4 enhancer can be functionally substituted by two copies of the TATA box proximal site. These and other results suggest that the E4 promoter may be comprised solely of multiple E4F1 binding sites and a TATA box. In addition to the E4 promoter, E4F1 interacts with other adenovirus early promoters and thus may be involved in the co-ordinate expression of E1a-inducible early viral genes.