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

Notch signaling dictates cell fate and critically influences cell proliferation, differentiation, and apoptosis in metazoans. Multiple factors at each step-ligands, receptors, signal transducers and effectors-play critical roles in executing the pleiotropic effects of Notch signaling. Ligand-binding results in proteolytic cleavage of Notch receptors to release the signal-transducing Notch intracellular domain (NICD). NICD migrates into the nucleus and associates with the nuclear proteins of the RBP-Jkappa family (also known as CSL or CBF1/Su(H)/Lag-1). RBP-Jkappa, when complexed with NICD, acts as a transcriptional activator, and the RBP-Jkappa-NICD complex activates expression of primary target genes of Notch signaling such as the HES and enhancer of split [E(spl)] families. HES/E(spl) is a basic helix-loop-helix (bHLH) type of transcriptional repressor, and suppresses expression of downstream target genes such as tissue-specific transcriptional activators. Thus, HES/E(spl) directly affects cell fate decisions as a primary Notch effector. HES/E(spl) had been the only known effector of Notch signaling until a recent discovery of a related but distinct bHLH protein family, termed HERP (HES-related repressor protein, also called Hey/Hesr/HRT/CHF/gridlock). In this review, we summarize the recent data supporting the idea of HERP being a new Notch effector, and provide an overview of the similarities and differences between HES and HERP in their biochemical properties as well as their tissue distribution. One key observation derived from identification of HERP is that HES and HERP form a heterodimer and cooperate for transcriptional repression. The identification of the HERP family as a Notch effector that cooperates with HES/E(spl) family has opened a new avenue to our understanding of the Notch signaling pathway.
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PMID:HES and HERP families: multiple effectors of the Notch signaling pathway. 1254 45

C-Repeat/drought responsive element binding factor (CBF1/DREB1b) is a well known transcriptional activator that is induced at low temperature and in turn induces the CBF regulon (CBF-targeted genes). We have cloned and characterized two CBF1-like cDNAs, CaCBF1A and CaCBF1B, from hot pepper. CaCBF1A and CaCBF1B were not produced in response to mechanical wounding or abscisic acid but were induced by low-temperature stress at 4 degrees . When plants were returned to 25 degrees , their transcript levels of the CBF1-like genes decreased markedly within 40 min. Long-term exposure to chilling resulted in continuous expression of these genes. The critical temperature for induction of CaCBF1A was between 10 and 15 degrees . Low temperature led to its transcription in roots, stems, leaves, fruit without seeds, and apical meristems, and a monoclonal antibody against it revealed a significant increase in CaCBF1A protein by 4 h at 4 degrees . Two-hybrid screening led to the isolation of an homeodomain leucine zipper (HD-Zip) protein that interacts with CaCBF1B. Expression of HD-Zip was elevated by low temperature and drought.
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PMID:Cold-inducible transcription factor, CaCBF, is associated with a homeodomain leucine zipper protein in hot pepper (Capsicum annuum L.). 1565 Mar 25

CSL (CBF1, Suppressor of Hairless, Lag-1) is a transcription factor that is responsible for activating the genes downstream of the Notch signalling pathway, a pathway that is essential for the development of the nervous system and the differentiation of the haematopoietic system among others. In the absence of Notch signalling, CSL represses transcription of Notch target genes, and following activation by Notch, CSL is converted into a transcriptional activator and activates transcription of the same genes. These two opposing functions of CSL are mediated through interactions with distinct protein complexes. The Notch signalling pathway and its crucial cofactor CSL can maintain cells in an undifferentiated state, and have therefore been associated with a growing list of cancers. In addition, CSL has been co-opted by Epstein-Barr virus to mediate viral and host gene transcription following infection.
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PMID:CSL: a notch above the rest. 1609 48

Transcription factors of the CSL family are the main mediators of the Notch signalling pathway. The CSL factor in Drosophila is called Suppressor of Hairless (Su(H)) and it has been shown that it acts as a transcriptional repressor in the absence of a Notch signal and as a transcriptional activator in its presence in several developmental contexts. Furthermore, recent data suggest that Su(H) can also activate and maintain transcription of some target genes in a Notch-independent manner. However, although it has been shown that the mammalian CSL ortholog, CBF1, acts as a repressor of transcription in cell culture experiments, so far in vivo evidence for such a function has been lacking. Moreover, it is not known whether CBF1 can activate transcription in a Notch-independent manner, just like Su(H). Here we have investigated these questions by introducing murine CBF1 (mCBF1) and asked whether it can functionally replace Su(H) during Drosophila development. We found that this is indeed the case. We show that mCBF1 can act as a repressor of transcription and can activate and maintain the expression of some target genes in a Notch-independent manner. Our results, therefore, indicate that CBF1 can exert these functions also in its normal context, that is during mammalian development.
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PMID:Functional analysis of murine CBF1 during Drosophila development. 1639 95

The Arabidopsis GCN5, ADA2a and ADA2b proteins are homologs of components of several yeast and animal transcriptional coactivator complexes. Previous work has implicated these plant coactivator proteins in the stimulation of cold-regulated gene expression by the transcriptional activator protein CBF1. Surprisingly, protein interaction studies demonstrate that the DNA-binding domain of CBF1 (and of a related protein, TINY), rather than its transcriptional activation domain, can bind directly to the Arabidopsis ADA2 proteins. The ADA2a and ADA2b proteins can also bind directly to GCN5 through their N-terminal regions (comparable to a region previously defined in yeast Ada2) and through previously unmapped regions in the middle of the ADA2 proteins, which bind to the HAT domain of GCN5. The ADA2 proteins enhance the ability of GCN5 to acetylate histones in vitro and enable GCN5 to acetylate nucleosomal histones. Moreover, GCN5 can acetylate the ADA2 proteins at a motif unique to the plant homologs and absent from fungal and animal homologs. We speculate that this modification may represent a novel autoregulatory mechanism for the plant SAGA-like transcriptional coactivator complexes.
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PMID:Physical and functional interactions of Arabidopsis ADA2 transcriptional coactivator proteins with the acetyltransferase GCN5 and with the cold-induced transcription factor CBF1. 1660 59

The CSL (CBF-1, Suppressor of Hairless, Lag-1) transcriptional factor is an important mediator of Notch signal transduction. It plays a key role in cell fate determination by cell-cell interaction. CSL functions as a transcriptional repressor before the activation of Notch signaling. However, once Notch signaling is activated, CSL is converted into a transcriptional activator. It remains unclear if CSL has any function during early development before neurogenesis, while transcriptional products exist from the maternal stage. Here, we analyzed the function of Xenopus Suppressor of Hairless (XSu(H)) using morpholino antisense oligonucleotides (MO), which interfere with the translation of transcripts. In Xenopus embryos, maternal transcripts of both XSu(H)1 and XSu(H)2 were ubiquitously observed until the blastula stage and thereafter only XSu(H)1 was zygotically transcribed. Knockdown experiments with MO demonstrated that XSu(H)2 depletion caused a decrease in the expression of the Xbrachyury, MyoD and JNK1 genes. Morphological and histological examinations indicated that XSu(H)2 depletion caused abnormal gastrulation, which resulted in severe defects of the notochord and somitic mesoderm. The effect of XSu(H)2-MO was completely rescued by co-injection of XSu(H)2 mRNAs, but not by XSu(H)1 mRNAs. XESR-1, a Notch signaling target gene, inhibited Xbrachyury expression. However, expression of the XESR-1 gene was not induced by depletion of XSu(H)2. Co-injection of the dominant-negative form of XESR-1 could not rescue the suppression of Xbrachyury expression in the XSu(H)2-depleted embryo. These results suggest that XSu(H)2 is involved in mesoderm formation and the cell movement of gastrula embryos in a different manner from the XESR-1-mediated Notch signaling pathway.
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PMID:XSu(H)2 is an essential factor for gene expression and morphogenesis of the Xenopus gastrula embryo. 1718 62

Thellungiella salsuginea, a wild crucifer that grows in subarctic Canada and is closely related to Arabidopsis thaliana, was examined for its suitability as a model plant for studies of tolerance to cold and freezing temperatures. Thellungiella completed its life cycle at 5 degrees C, demonstrating that temperature-sensitive processes such as seed germination and the production of pollen and seeds were resistant to cold temperatures. Moreover, the plant exhibited dramatically different vegetative and flowering phenotypes in response to growth at cold temperature and shifts to cold temperature. Northern analyses showed that genes induced by cold in Arabidopsis, including CBF1, the transcriptional activator for the cold-regulated (COR) genes COR15a and COR47, were also expressed in Thellungiella. Freezing tolerance, assayed by the regrowth of intact plants, increased from -13.0 to -18.5 degrees C after cold treatment. The plants lacked endogenous ice nucleation or anti-freeze activity, indicating a potential for supercooling. As a close relative to Arabidopsis, Thellungiella exhibits extreme cold tolerance and should be an important model system in the elucidation of stress tolerance mechanisms.
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PMID:Thellungiella: an Arabidopsis-related model plant adapted to cold temperatures. 1740 31

Plants have evolved robust mechanisms to respond and adapt to unfavorable environmental conditions, such as low temperature. The C-repeat/drought-responsive element binding factor CBF1/DREB1b gene encodes a transcriptional activator transiently induced by cold that controls the expression of a set of genes responding to low temperature (the CBF regulon). Constitutive expression of CBF1 confers freezing tolerance but also slows growth. Here, we propose that low temperature-induced CBF1 expression restrains growth at least in part by allowing the accumulation of DELLAs, a family of nuclear growth-repressing proteins, the degradation of which is stimulated by gibberellin (GA). We show that cold/CBF1 enhances the accumulation of a green fluorescent protein (GFP)-tagged DELLA protein (GFP-RGA) by reducing GA content through stimulating expression of GA-inactivating GA 2-oxidase genes. Accordingly, transgenic plants that constitutively express CBF1 accumulate less bioactive GA and as a consequence exhibit dwarfism and late flowering. Both phenotypes are suppressed when CBF1 is expressed in a line lacking two DELLA proteins, GA-INSENSITIVE and REPRESSOR OF GA1-3. In addition, we show that DELLAs contribute significantly to CBF1-induced cold acclimation and freezing tolerance by a mechanism that is distinct from the CBF regulon. We conclude that DELLAs are components of the CBF1-mediated cold stress response.
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PMID:The cold-inducible CBF1 factor-dependent signaling pathway modulates the accumulation of the growth-repressing DELLA proteins via its effect on gibberellin metabolism. 1875 56

C-repeat/dehydration-responsive element binding factor (CBF) is a transcription factor regulating cold response in plants, of which little is known in fruits. We showed a double-peak expression pattern of Lycopersicon esculentum putative transcriptional activator CBF1 (LeCBF1) in mature green fruit. The peaks appeared at 2 and 16 h after subjection to cold storage (2 degrees C). The second peak was coincident with, and thus caused by a peak in endogenous ethylene production. We showed that LeCBF1 expression was regulated by exogenous ethylene and 1-methylcyclopropene, and was not expressed without cold induction. LeCBF1 expression was different in the five maturation stages of fruits, but expression peaked at 2 h at all stages.
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PMID:Ethylene and cold participate in the regulation of LeCBF1 gene expression in postharvest tomato fruits. 1976 36

The plant hormone ethylene affects myriad developmental processes ranging from seed germination to organ senescence, and plays a crucial role in plant resistance to environmental stresses. The C-repeat/dehydration-responsive element binding factor genes (CBF1-3) are transcriptional activators involved in plant low-temperatures responses; their overexpression enhances frost tolerance, but also has various pleiotropic effects on growth and development, mainly growth retardation and delay of flowering and senescence. We found that overexpression of CBF2 in Arabidopsis suppressed leaf tissue responsiveness to ethylene as compared with wild-type plants, as manifested in significantly delayed senescence and chlorophyll degradation. In wild-type plants, exposure to ethylene at 0.1 microl.l(-1) for 48 h caused 50% reduction in chlorophyll levels as compared to leaves held in air alone, whereas CBF2-overexpressing plants required an ethylene concentration of 10.0 microl.l(-1) to cause the same effect. Furthermore, continuous exposure to ethylene at 1.0 microl.l(-1) reduced chlorophyll content in wild-type leaves by 50% after 42 h but took 72 h in CBF2-overexpressing plants. Transcript profiling of ethylene receptors and signal transduction genes in leaves of wild-type and CBF2-overexpressing plants, by means of the Affymetrix ATH1 genome array, revealed only minor differences in gene expression patterns - insufficient to explain the observed responsiveness differences. Nevertheless, we found that overexpression of CBF2 significantly increased transcript levels of 17 ABA biosynthetic and responsive genes and, thus, may have affected leaf responsiveness to ethylene via contrasting interactions with other hormones, mainly ABA. Overall, the current findings suggest that overexpression of the CBF2 transcriptional activator in Arabidopsis may, at least in part, contribute to the observed delay of leaf senescence and enhanced plant fitness by suppressing leaf responsiveness to stress-regulated ethylene.
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PMID:Overexpression of the CBF2 transcriptional activator in Arabidopsis suppresses the responsiveness of leaf tissue to the stress hormone ethylene. 2063 6


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