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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent efforts have defined a cis-acting DNA regulatory element in plants, the C-repeat/dehydration responsive element (DRE), that stimulates transcription in response to low temperature and water deficit. Here we report the isolation of an Arabidopsis thaliana cDNA that encodes a C-repeat/DRE binding factor, CBF1 (C-repeat/DRE Binding Factor 1). Analysis of the deduced CBF1 amino acid sequence indicates that the protein has a molecular mass of 24 kDa, a potential nuclear localization sequence, and a possible acidic activation domain. CBF1 also has an AP2 domain, which is a DNA-binding motif of about 60 aa present in the Arabidopsis proteins APETALA2, AINTEGUMENTA, and TINY; the tobacco ethylene response element binding proteins; and numerous other plant proteins of unknown function. The transcript levels for CBF1, which appears to be a single or low copy number gene, did not change appreciably in plants exposed to low temperature or in detached leaves subjected to water deficit. Binding of CBF1 to the C-repeat/DRE was demonstrated in gel shift assays using recombinant CBF1 protein expressed in Escherichia coli. Moreover, expression of CBF1 in yeast was found to activate transcription of reporter genes containing the C-repeat/DRE as an upstream activator sequence but not mutant versions of the DNA element. We conclude that CBF1 can function as a transcriptional activator that binds to the C-repeat/DRE DNA regulatory element and, thus, is likely to have a role in cold- and dehydration-regulated gene expression in Arabidopsis.
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PMID:Arabidopsis thaliana CBF1 encodes an AP2 domain-containing transcriptional activator that binds to the C-repeat/DRE, a cis-acting DNA regulatory element that stimulates transcription in response to low temperature and water deficit. 902 78

Cold-induced expression of the Arabidopsis COR (cold-regulated) genes is mediated by a DNA regulatory element termed the CRT (C-repeat)/DRE (dehydration-responsive element). Recently, we identified a transcriptional activator, CBF1, that binds to the CRT/DRE and demonstrated that its overexpression in transgenic Arabidopsis plants at non-acclimating temperatures induces COR gene expression and increases plant freezing tolerance. Here we report that CBF1 belongs to a small family of closely related proteins which includes CBF2 and CBF3. DNA sequencing of an 8.7 kb region of the Arabidopsis genome along with genetic mapping experiments indicated that the three CBF genes are organized in direct repeat on chromosome 4 at 72.8 cM, closely linked to molecular markers PG11 and m600. Like CBF1, both CBF2 and CBF3 activated expression of reporter genes in yeast that contained the CRT/DRE as an upstream activator sequence. The transcript levels for all three CBF genes increased within 15 min of transferring plants to low temperature, followed by accumulation of COR gene transcripts at about 2 h. CBF transcripts also accumulated rapidly in response to mechanical agitation. The promoter regions of the CBF genes do not contain the CRT sequence, CCGAC, and overexpression of CBF1 did not have a detectable effect on CBF3 transcript levels, suggesting that the CBF gene family is not subject to autoregulation. We propose that cold-induced expression of CRT/DRE-containing COR genes involves a low temperature-stimulated signalling cascade in which CBF gene induction is an early event.
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PMID:Low temperature regulation of the Arabidopsis CBF family of AP2 transcriptional activators as an early step in cold-induced COR gene expression. 988 Nov 63

We have identified two genes from Arabidopsis that show high similarity with CBF1, a gene encoding an AP2 domain-containing transcriptional activator that binds to the low-temperature-responsive element CCGAC and induces the expression of some cold-regulated genes, increasing plant freezing tolerance. These two genes, which we have named CBF2 and CBF3, also encode proteins containing AP2 DNA-binding motifs. Furthermore, like CBF1, CBF2 and CBF3 proteins also include putative nuclear-localization signals and potential acidic activation domains. The CBF2 and CBF3 genes are linked to CBF1, constituting a cluster on the bottom arm of chromosome IV. The high level of similarity among the three CBF genes, their tandem organization, and the fact that they have the same transcriptional orientation all suggest a common origin. CBF1, CBF2, and CBF3 show identical expression patterns, being induced very rapidly by low-temperature treatment. However, in contrast to most of the cold-induced plant genes characterized, they are not responsive to abscisic acid or dehydration. Taken together, all of these data suggest that CBF2 and CBF3 may function as transcriptional activators, controlling the level of low-temperature gene expression and promoting freezing tolerance through an abscisic acid-independent pathway.
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PMID:The Arabidopsis CBF gene family is composed of three genes encoding AP2 domain-containing proteins whose expression Is regulated by low temperature but not by abscisic acid or dehydration. 995 41

A transcriptional activator, CBF1, from Arabidopsis thaliana, which has the AP2 domain for DNA binding and regulates the cold acclimation response, was overexpressed in Escherichia coli, purified, and characterized. Analyses of the interaction between CBF1 and the C-repeat/dehydration-responsive element by fluorescence measurement showed that CBF1 binds to C-repeat/dehydration-responsive element as a monomer irrespective of the temperature. CD spectra of the intact and truncated CBF1 proteins (1-213, 41-213, 41-157, and 41-146) were measured to examine the temperature-dependent changes of the secondary structure of CBF1. The results suggested that the CBF1 protein has regions exhibiting reversible cold denaturation in the range between 30 and -5 degrees C and also has a region exhibiting thermal denaturation between 40 and 60 degrees C. This cold denaturation occurred in both the N-terminal and acidic regions. The thermal denaturation occurred in the region encompassing the AP2 domain. The difference between the retention time of CBF1 at 4 degrees C and that at 25 degrees C in gel filtration, and the decrease of the sedimentation coefficient, s20,w, caused by the temperature change from 25 to 3 degrees C, strongly suggested that the cold denaturation was accompanied by the extension of the molecule. The possible cold denaturation observed here might be a physiologically important structural response of CBF1 to cold stress.
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PMID:Characterization of the transcriptional activator CBF1 from Arabidopsis thaliana. Evidence for cold denaturation in regions outside of the DNA binding domain. 1034 58

The maize abscisic acid (ABA)-responsive gene rab28 has been shown to be ABA-inducible in embryos and vegetative tissues, expression being mostly restricted to vascular elements during late embryogenesis. In the course of an expressed sequence tags (ESTs) programme, we have isolated an Arabidopsis thaliana gene, Atrab28, encoding the orthologue of maize rab28. The Atrab28 cDNA is 1090 bp long, including a poly(A)+ stretch, and encodes a polypeptide of 262 amino acids. Atrab28 antibody against the recombinant protein recognizes a polipeptide of about 30 kDa and pI 6, in close agreement with the predicted molecular mass and pI. As for maize rab28, expression studies with Atrab28 revealed high specificity for embryo tissues, transcription being stimulated by the transcriptional activator abi3. In contrast, Atrab28 was not induced in vegetative tissues by ABA, osmotic stress or dehydration. The expression of Atrab28 mRNA and the accumulation of Atrab28 protein was largely restricted to provascular tissues of mature embryos and in the seed coat outer tegument and embryo and silique epidermis, as revealed by in situ hybridization and immunocytochemistry with anti-Atrab28 antibodies.
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PMID:Expression and cellular localization of Atrab28 during arabidopsis embryogenesis. 1041 13

A HvCBF1 cDNA encoding an AP2 domain-containing protein was isolated from barley leaves. Expression of HvCBF1 was induced in barley leaves by exposure to a low temperature (2 degrees C), but not by drought or abscisic acid (ABA) treatment. Functional analysis showed that HvCBF1 was a transcriptional activator, capable of activating expression of reporter genes driven by a cold- and drought-responsive HVA1s promoter in barley leaves. Transactivation analysis of HvCBF1 on a number of synthetic oligonucleotides containing potential C-repeat (CRT)/dehydration-responsive element (DRE) derived from cold-responsive barley genes revealed that HvCBF1 interacted much more efficiently with a GCCGAC motif than a previously identified barley low-temperature-responsive element (LTRE), CCGAAA. A detailed base-substitution mutagenesis study revealed that only the CGAC sequence of the GCCGAC motif was highly conserved for interacting with HvCBF1. The promoter activity of the mutant motifs, ACCGAC and GTCGAC, was 36% and 75% of that of the GCCGAC motif, respectively. The base composition surrounding the GCCGAC motif also had a significant effect on the efficiency of the motif. These data suggest that barley HvCBF1 protein interacts with the (G/a)(C/t)CGAC motif and is involved in regulation of cold-responsive genes in barley via an ABA-independent signal transduction pathway.
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PMID:An AP2 domain transcription factor HvCBF1 activates expression of cold-responsive genes in barley through interaction with a (G/a)(C/t)CGAC motif. 1215 Oct 96

An HvCBF2 cDNA was isolated from barley leaves. It encoded a protein containing an AP2 DNA-binding domain homologous to C-repeat (CRT)/dehydration-responsive element (DRE) binding factors (CBF/DREB1). In contrast to the previously reported cold-inducible CBF/DREB1 genes, HvCBF2 was expressed in barley leaves under non-stress conditions. Only a transient increase in the HvCBF2 transcript level was observed during cold treatment. Transactivation analysis showed that HvCBF2 was a transcriptional activator, capable of activating expression of a reporter gene driven by a low-temperature and drought-responsive HVA1s promoter in barley leaves. The activity of HvCBF2 as a transcriptional activator was upregulated by low temperature. DNA-binding analysis revealed that HvCBF2 did not bind to the CRT/DRE motif at 30 degrees C. A low, but detectable, binding activity was observed at 25 degrees C and the binding activity gradually increased as the temperature decreased. The binding activity at 0 degrees C was the highest and more than 10 times higher than that at 25 degrees C. The activation and inactivation of HvCBF2 activity were reversible and were achieved in a cell-free system simply by temperature change. Analysis of the binding sequence showed that HvCBF2 bound to a (G/a)(T/c)CGAC core motif, where the lower-case letters are less efficient bases. These data suggest that HvCBF2 is a transcription factor interacting with the core CRT/DRE motif containing a preferred sequence of GTCGAC and its DNA-binding activity is regulated by temperature. This represents a new type of activation mechanism for transcriptional activators.
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PMID:The DNA-binding activity of an AP2 transcriptional activator HvCBF2 involved in regulation of low-temperature responsive genes in barley is modulated by temperature. 1253 50

Apetala2/ethylene-responsive factor (AP2/ERF) proteins are AP2 domain-containing transcription factors and form the second largest transcription factor family in plants. Biological functions of many of these AP2 proteins are still unknown. Here, we report the characterisation of a novel member of the AP2/ERF superfamily, dehydration-responsive factor 1 (HvDRF1) from barley, and its role in abscisic acid (ABA)-mediated gene regulation. The expression of HvDRF1 was upregulated in barley leaves and roots under drought, salt or ABA treatment, and in embryos during seed maturation. Three forms of HvDRF1 transcripts were produced through alternative splicing, two of which encoded AP2 proteins. This alternative splicing pattern was also observed in a wheat homologue gene, TaDRF1. Both of HvDRF1 AP2 proteins acted as transcriptional activators, capable of activating the promoter activity of an ABA-inducible HVA1s in barley. In vitro DNA-binding analysis using synthetic oligonucleotides revealed that HvDRF1 AP2 protein bound preferably to a CT-rich element (T(T/A)ACCGCCTT). HvDRF1 activity on the activation of HVA1s expression in barley leaves was markedly enhanced by HvABI5 (a bZIP transcription factor), ABA or drought treatment. These results indicate that the HvDRF1 transcriptional activator co-operates with other ABA-responsive factors in the upregulation of stress gene expression through an ABA-dependent pathway.
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PMID:HvDRF1 is involved in abscisic acid-mediated gene regulation in barley and produces two forms of AP2 transcriptional activators, interacting preferably with a CT-rich element. 1473 Dec 54

Ethylene responsive factors (ERFs) are important plant-specific transcription factors, some of which have been demonstrated to interact with the ethylene-responsive GCC box and the dehydration-responsive element (DRE); however, data on the roles of ERF proteins in connection with various signaling pathways are limited. In this research, we used the GCC box, an essential cis-acting element responsive to ethylene and methyl jasmonate (MeJA), as bait in a yeast one-hybrid system to isolate transcription factors from tomato (Lycopersicon esculentum Mill.). One of the cDNAs, which was designated Jasmonate and Ethylene Response Factor 1 (JERF1), encodes an ERF protein, containing a conserved ERF DNA-binding motif and functioning as a transcriptional activator in yeast through targeting to the nucleus in onion (Allium cepa L.) epidermal cells. Biochemical analysis revealed that JERF1 bound not only to the GCC box but also to the DRE sequence. Expression of the JERF1 gene in tomato was induced by ethylene, MeJA, abscisic acid (ABA) and salt treatment, indicating that JERF1 might act as a connector among different signal transduction pathways. Further research with transgenic JERF1 tobacco (Nicotiana tabacum L.) plants indicated that overexpressing JERF1 activated expression of GCC box-containing genes such as osmotin, GLA, Prb-1b and CHN50 under normal growth conditions, and subsequently resulted in enhanced tolerance to salt stress, suggesting that JERF1 modulates osmotic tolerance by activation of downstream gene expression through interaction with the GCC box or DRE.
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PMID:The ethylene-, jasmonate-, abscisic acid- and NaCl-responsive tomato transcription factor JERF1 modulates expression of GCC box-containing genes and salt tolerance in tobacco. 1530 Apr 40

Calmodulin (CaM), a ubiquitous calcium-binding protein, regulates diverse cellular functions by modulating the activity of a variety of enzymes and proteins. Plants express numerous CaM isoforms that exhibit differential activation and/or inhibition of CaM-dependent enzymes in vitro. However, the specific biological functions of plant CaM are not well known. In this study, we isolated a cDNA encoding a CaM binding transcription factor, MYB2, that regulates the expression of salt- and dehydration-responsive genes in Arabidopsis. This was achieved using a salt-inducible CaM isoform (GmCaM4) as a probe from a salt-treated Arabidopsis expression library. Using domain mapping, we identified a Ca2+-dependent CaM binding domain in MYB2. The specific binding of CaM to CaM binding domain was confirmed by site-directed mutagenesis, a gel mobility shift assay, split ubiquitin assay, and a competition assay using a Ca2+/CaM-dependent enzyme. Interestingly, the specific CaM isoform GmCaM4 enhances the DNA binding activity of AtMYB2, whereas this was inhibited by a closely related CaM isoform (GmCaM1). Overexpression of Gm-CaM4 in Arabidopsis up-regulates the transcription rate of AtMYB2-regulated genes, including the proline-synthesizing enzyme P5CS1 (Delta1-pyrroline-5-carboxylate synthetase-1), which confers salt tolerance by facilitating proline accumulation. Therefore, we suggest that a specific CaM isoform mediates salt-induced Ca2+ signaling through the activation of an MYB transcriptional activator, thereby resulting in salt tolerance in plants.
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PMID:Direct interaction of a divergent CaM isoform and the transcription factor, MYB2, enhances salt tolerance in arabidopsis. 1556 82


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