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CREB-binding protein and p300/CBP-associated factor are transcriptional coactivators of the p53 tumor suppressor protein.

The structurally related transcriptional coactivators p300 and CBP possess histone acetyltransferase activity and associate with P/CAF, which is also a histone acetyltransferase. CBP and p300 have properties of tumor suppressor proteins; their interaction with P/CAF is disrupted by the adenoviral E1A oncoprotein, and the genes encoding CBP and p300 are mutated in human cancer. We observed a physical interaction between the transactivation domain of the p53 tumor suppressor protein and CBP. Furthermore, CBP and P/CAF enhanced the ability of p53 to activate expression of the endogenous p21(cip1/waf1) gene, whereas E1A and dominant negative CBP mutants suppressed p53-dependent p21(cip1/waf1) expression. These studies link two tumor suppressor families and provide a framework for understanding the molecular mechanism by which p53 activates transcription.

Binding Sites↗

CREB phosphorylation and c-Fos expression in the hippocampus of rats during acquisition and recall of a socially transmitted food preference.

In the present study, phosphorylation of cAMP-response element binding protein (pCREB) and expression of c-Fos were measured in the dorsal and ventral hippocampus, as well as in a control region, the retrosplenial cortex, of rats following acquisition and recall of a socially transmitted food preference (STFP). Behavioral analyses revealed that STFP-trained rats showed a stronger preference for the demonstrated food than did rats in social-control or odor-control conditions. Rats in a social + odor control condition displayed an intermediate preference that was not significantly different from either STFP-trained rats or the social- or odor-controls. Immunocytochemical analyses revealed increased pCREB-immunoreactivity (ir) in the ventral hippocampus of STFP-trained rats in comparisons with rats in all three control conditions and increased pCREB-ir in the dorsal hippocampus in comparisons with the social- and odor-control conditions. In contrast, c-Fos-ir was greater in the dorsal hippocampus of STFP-trained rats in comparisons with all three control conditions and greater in the ventral hippocampus than rats in the social- and odor-control conditions. Comparisons of pCREB-ir and c-Fos-ir were made also between STFP-trained rats and social-controls following either acquisition or a 48-h recall test. c-Fos-ir was greater in STFP-trained rats after both acquisition and recall, whereas pCREB was greater after recall only. There were no differences in either c-Fos-ir or pCREB-ir in comparisons between trained and control rats in the retrosplenial cortex. The current results indicate that the activity of transcription factors in the hippocampus is related to both acquisition and retention of a socially transmitted food preference.

Animals↗

cAMP induces phosphorylation of a 40-kDa nuclear protein which is distinct from CREB during chondrogenesis of chick limb bud mesenchymal cells in vitro.

We examined the effect of cAMP on the phosphorylation of intracellular proteins in cultured chondroblasts to understand the stimulatory role of intracellular cAMP in chondrogenesis of chick limb bud mesenchymal cells. A 40-kDa protein was remarkably phosphorylated by cAMP and the phosphorylation was completely blocked by an inhibitor of cAMP-dependent protein kinase. The phosphorylation of the 40-kDa protein was maximum at early stage of chondrogenesis (i.e., 24 hr of culture) which is consistent with the changes in the level of intracellular cAMP. The 40-kDa phosphoprotein was exclusively located in the nuclear parts of chondroblast but distinct from cAMP response element binding protein.

Animals↗

Transcription of Djun from D. melanogaster is positively regulated by DTF-1, AP-1, and CREB binding sites.

Djun is the homolog of the mammalian proto-oncogene jun in D. melanogaster, where it encodes a component of an AP-1-like nuclear DNA binding protein, or transcription factor. Djun, unlike its vertebrate counterparts, contains an intron in its 5' noncoding region. The expression of Djun in cultured Schneider line 2 cells is controlled by multiple cis-acting elements in its promoter region and the 5' noncoding region of the transcription unit. A 43-bp 5' upstream promoter region is necessary for the transcription activity of Djun. Deletion of this fragment decreased transcriptional activity by 67-fold. This region includes a TATA box and a sequence similar to the Drosophila transcription factor 1 (DTF-1) consensus sequence (GCAACAT/GC/C). A large DNase I footprint covering both the DTF-1 binding site and the TATA box was detected in this region when incubated with nuclear extract from Drosophila embryos, suggesting interactions with related transcription factors. This 43-bp sequence alone, containing the DTF-1 binding site and TATA box, however, is not sufficient for transcription activity. An 80-bp sequence including the start of transcription has considerable basal activity. An intragenic region containing an AP-1 site and a CRE site modulates or fine tunes activity of the promoter. Its activity as an enhancer is reduced when moved upstream in either orientation. An extragenic region containing two AP-1 sites similarly affects promoter activity.

Animals↗

Comparison of expression patterns between CREB family transcription factor OASIS and proteoglycan core protein genes during murine tooth development.

The transcription factor OASIS gene, which encodes for a CREB/ATF family member, is specifically expressed in the salivary gland, the cartilage and the tooth germs of the mouse embryo. In the present study, the expression patterns were compared between OASIS mRNA and major vertebrate proteoglycans, which might be the downstream genes of OASIS in the tooth germs of mouse first mandibular molars, through in situ hybridization histochemistry. OASIS mRNA expression was observed in the inner enamel epithelium during the cap and bell stages (E14.5-E18.5) in the preodontoblasts during differentiation stage (E18.5-P0) and in the differentiating odontoblasts during the early secretory stage (P2.5-P4.5). Proteoglycans (versican, decorin, biglycan, glypican, syndecan-1, and syndecan-3) were expressed in the tooth germs in various patterns. Decorin, biglycan, syndecan-1 and syndecan-3 showed gene expressions overlapping with OASIS. Especially the expression pattern of decorin and syndecan-3 coincided temporally and spatially exactly with that of OASIS. These results suggest that the OASIS gene might be related to proteoglycan expression and may play an important role in the differentiation of the odontoblast and cells in inner enamel epithelium.

Aggrecans↗

Effects of aging on light-induced phase-shifting of circadian behavioral rhythms, fos expression and CREB phosphorylation in the hamster suprachiasmatic nucleus.

Aging is associated with a variety of alterations in circadian rhythms, including changes in the response to environmental stimuli. The underlying causes for these age-related changes in the circadian system remain unknown. Recent studies have demonstrated that light induces the expression of Fos and phosphorylation of the cyclic-AMP response element-binding protein in the rodent suprachiasmatic nuclei, the location of a master circadian pacemaker in mammals, suggesting that these transcription factors may mediate the effects of light on the circadian clock. The purpose of this study was to determine the effects of aging upon light-induced phase-shifting of circadian locomotor activity rhythms, Fos protein expression and cyclic-AMP response element-binding protein phosphorylation in the suprachiasmatic nuclei. Young (three to four months) and old (18-22 months) male golden hamsters free-running in constant darkness were exposed to 5-min monochromatic light pulses of different irradiance levels, at circadian time 19, after which either steady-state phase shifts of locomotor activity rhythms were measured, or else immunocytochemistry for Fos or for phospho-cyclic-AMP response element-binding protein was performed. Old hamsters were approximately 20 times less sensitive to the phase-shifting effects of light on the activity rhythm, and the photic irradiance threshold for Fos-like immunoreactivity induction in the suprachiasmatic nuclei was elevated when compared to young animals. Aging was also associated with a deficit in cyclic-AMP response element-binding protein phosphorylation by light. These data indicate that there are dramatic changes in light-activated molecular responses in the suprachiasmatic nuclei of old hamsters, and suggest that these molecular changes may underlie age-related changes in the effects of light on the circadian clock system.

Age Factors↗

A broad bean cDNA clone encoding a DNA-binding protein resembling mammalian CREB in its sequence specificity and DNA methylation sensitivity.

A plant cDNA has been cloned that encodes a DNA-binding protein displaying a nucleotide (nt) sequence specificity similar to that of the mammalian cyclic AMP response element-binding protein/activating transcription factor (CREB/ATF) family of mammalian proteins. This cDNA was cloned in Escherichia coli from a broad bean (Vicia faba) cDNA expression library using a recognition site probe. The deduced amino acid (aa) sequence of the recombinant cDNA-encoded protein, called VBP1, has a basic region adjacent to a leucine zipper motif, of the type seen in the DNA-binding domains of many eukaryotic DNA-binding proteins, including mammalian CREB/ATF. Although this aa sequence has homology to regions of deduced aa sequences of other cloned plant cDNAs, it is distinct in both the derived primary structure and in its nt sequence specificity. VBP1, as well as proteins in nuclear extracts of V. faba with similar nt sequence specificity, have their binding to DNA suppressed more than tenfold by cytosine methylation at the CREB/ATF consensus sequence.

Amino Acid Sequence↗

HMG-CoA reductase inhibitors induce COX-2 gene expression in murine macrophages: role of MAPK cascades and promoter elements for CREB and C/EBPbeta.

Except functioning as lipid-lowering agents, HMG-CoA inhibitors, statins, are good tools to clarify the signaling role of small G proteins. In this study, we found in murine RAW264.7 macrophages, statins within 1-30 microM stimulated COX-2 gene transcription and PGE(2) formation, displaying potencies as lovastatin > fluvastatin > atorvastatin >> pravastatin. Transfection experiments with COX-2 promoter construct showed the necessity of C/EBPbeta and CRE promoter sites, but not NF-kappaB promoter site. Effects of statins on the activation of COX-2 promoter, induction of COX-2 protein, and PGE(2) production were all prevented by mevalonate and prenylated metabolites, FPP and GGPP. Consistent with the effect of statins, manumycin A, farnesyltransferase inhibitor, and geranylgeranyltransferase inhibitor increased PGE(2) production and COX-2 induction. Likewise, toxin B, an inhibitor of Rho family members, caused a prominent COX-2 induction. Results also indicated that tyrosine kinase, ERK, and p38 MAPK play essential roles in statin action. Taken together, these results not only demonstrate a unique action of statins in the upregulation of COX-2 expression in macrophages, but also suggest a negative role controlled by small G proteins in COX-2 gene regulation. Removal of this negative control by impairing G protein prenylation with statins leads to MAPKs activation and promotes COX-2 gene expression through the activation at CRE and C/EBPbeta sites.

Animals↗

Regulation of cyclooxygenase-2 expression by iloprost in human vascular smooth muscle cells. Role of transcription factors CREB and ICER.

Prostaglandin-endoperoxide synthase-2 (PGH-synthase) or cyclooxygenase-2 (COX-2) is inducible by a variety of stimuli, e.g. inflammatory mediators, growth factors and hormones and is believed to be responsible for the majority of inflammatory prostanoid production. Moreover, it has been demonstrated that COX-2 contributes substantially to prostacyclin-synthesis in patients with atherosclerosis. In this study, we demonstrate an up-regulation of COX-2 mRNA, protein and product formation by the prostacyclin-mimetic iloprost in human vascular smooth muscle cells (hSMC). COX-2 mRNA expression was induced transiently between 1 and 6 hr and returned to basal levels after 16 hr of iloprost stimulation. COX-2 protein was induced concomitantly between 3 and 6 hr of iloprost stimulation. This was accompanied by an increase in PGI(2) formation. Forskolin, a direct activator of adenylyl cyclase, and dibutyryl cAMP, a cell-permeable cAMP analogue-induced COX-2 mRNA, suggesting a cAMP-dependent COX-2 expression in hSMC. Iloprost-induced COX-2 protein expression and PGI(2) formation was synergistically elevated by co-stimulation with the phorbolester PMA (phorbol-12-myristate-13-acetate). It is concluded, that the observed up-regulation of COX-2 with subsequent release of newly synthesized PGI(2) and the synergistic effect of iloprost and phorbolester on PGI(2) formation provide a positive feedback of prostaglandins on their own synthesizing enzyme. This might be important for control of hSMC proliferation, migration and differentiation as well as inhibition of platelet aggregation.

Cyclic AMP↗

NGF-dependent and tissue-specific transcription of vgf is regulated by a CREB-p300 and bHLH factor interaction.

Neurotrophins support neuronal survival, development, and plasticity through processes requiring gene expression. We studied how vgf target gene transcription is mediated by a critical promoter region containing E-box, CCAAT and cAMP response element (CRE) sites. The p300 acetylase was present in two distinct protein complexes bound to this region. One complex, containing HEB (ubiquitous basic helix-loop-helix (bHLH)), bound the promoter in non-neuronal cells and was involved in repressing vgf expression. Neurotrophin-dependent transcription was mediated by the second complex, specific for neuronal cells, which included CRE binding protein and MASH1 (neuro-specific bHLH), bound the CCAAT motif, and was target of neurotrophin signalling. The interaction, mediated by p300, of different transcription factors may add specificity to the neurotrophin response.

3T3 Cells↗