Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cAMP response element binding protein CREB activates the transcription of genes in response to phosphorylation by cAMP-dependent protein kinase A (PKA) and other protein kinases. Phosphorylated CREB activates transcription by recruiting transcriptional co-activators such as the CREB binding protein. Here, we describe experiments that analyze the effects of phosphorylation on the DNA binding affinity of CREB and the structural characteristics of the CREB/DNA complex in solution. Analysis of deletion mutants of CREB indicate that amino acid sequences within the transactivation domain promote high-affinity binding of CREB to fluorescently labeled oligonucleotides containing cAMP response elements. In vitro experiments indicate that phosphorylation is processive between PKA as the initial kinase and glycogen synthase kinase-3 (GSK-3) but not casein kinase II as the secondary kinase. Fluorescent electrophoretic mobility shift assays show that phosphorylation by PKA results in a 3-5-fold increase in the binding affinity of CREB to both the symmetrical somatostatin CRE (SMS-CRE) and the asymmetric somatostatin upstream element (SMS-UE). Processive phosphorylation of CREB by GSK-3 attenuates the enhanced DNA binding in response to PKA thus acts as an inhibitor of PKA-induced binding. Ferguson plot analyses demonstrate that phosphorylation of CREB by PKA and GSK-3 result in an increase in the spherical size and the net positive surface charge of the CREB/DNA complex. Moreover, these analyses uncovered the unexpected finding that CREB associates as a tetramer both in the presence and absence of DNA. These findings suggest a model by which phosphorylation of CREB alters the secondary structure and charge characteristics of the CREB/DNA complex resulting in an alteration in binding affinity.
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PMID:Phosphorylation of the cAMP response element binding protein CREB by cAMP-dependent protein kinase A and glycogen synthase kinase-3 alters DNA-binding affinity, conformation, and increases net charge. 952 99

The cyclic AMP (cAMP)-responsive factor CREB induces target gene expression via constitutive (Q2) and inducible (KID, for kinase-inducible domain) activation domains that function synergistically in response to cellular signals. KID stimulates transcription via a phospho (Ser133)-dependent interaction with the coactivator paralogs CREB binding protein and p300, whereas Q2 recruits the TFIID complex via a direct association with hTAF(II)130. Here we investigate the mechanism underlying cooperativity between the Q2 domain and KID in CREB by in vitro transcription assay with naked DNA and chromatin templates containing the cAMP-responsive somatostatin promoter. The Q2 domain was highly active on a naked DNA template, and Ser133 phosphorylation had no additional effect on transcriptional initiation in crude extracts. Q2 activity was repressed on a chromatin template, however, and this repression was relieved by the phospho (Ser133) KID-dependent recruitment of p300 histone acetyltransferase activity to the promoter. In chromatin immunoprecipitation assays of NIH 3T3 cells, cAMP-dependent recruitment of p300 to the somatostatin promoter stimulated acetylation of histone H4. Correspondingly, overexpression of hTAFII130 potentiated CREB activity in cells exposed to cAMP, but had no effect on reporter gene expression in unstimulated cells. We propose that cooperativity between the KID and Q2 domains proceeds via a chromatin-dependent mechanism in which recruitment of p300 facilitates subsequent interaction of CREB with TFIID.
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PMID:Chromatin-dependent cooperativity between constitutive and inducible activation domains in CREB. 1168 82

p300/CREB binding protein-associated factor (PCAF) regulates gene expression by acting through histone acetylation and as a transcription coactivator. Although histone acetyltransferases were involved in the toxicity induced by amyloid-beta (Abeta) peptides, nothing is known about PCAF. We here analyzed the sensitivity of PCAF knockout (KO) mice to the toxic effects induced by i.c.v. injection of Abeta(25-35) peptide, a nontransgenic model of Alzheimer's disease. PCAF wild-type (WT) and KO mice received Abeta(25-35) (1, 3 or 9 nmol) or scrambled Abeta(25-35) (9 nmol) as control. After 7 days, Abeta(25-35) toxicity was measured in the hippocampus of WT mice by a decrease in CA1 pyramidal cells and increases in oxidative stress, endoplasmic reticulum stress and induction of apoptosis. Memory deficits were observed using spontaneous alternation, water-maze learning and passive avoidance. Non-treated PCAF KO mice showed a decrease in CA1 cells and learning alterations. However, Abeta(25-35) injection failed to induce toxicity or worsen the deficits. This resistance to Abeta(25-35) toxicity did not involve changes in glutamate or acetylcholine systems. Examination of enzymes involved in Abeta generation or degradation revealed changes in transcription of presenilins, activity of neprilysin (NEP) and an absence of Abeta(25-35)-induced regulation of NEP activity in PCAF KO mice, partly due to an altered expression of somatostatin (SRIH). We conclude that PCAF regulates the expression of proteins involved in Abeta generation and degradation, thus rendering PCAF KO insensitive to amyloid toxicity. Modulating acetyltransferase activity may offer a new way to develop anti-amyloid therapies.
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PMID:Mice knock out for the histone acetyltransferase p300/CREB binding protein-associated factor develop a resistance to amyloid toxicity. 2021 49