Regulation of cAMP-responsive Element-binding Protein-mediated Transcription by the SNF2/SWI-related Protein, SRCAP

Abstract

SRCAP (SNF2-related CPB activator protein) belongs to the SNF2 family of proteins whose members participate in various aspects of transcriptional regulation, including chromatin remodeling. It was identified by its ability to bind to cAMP-responsive-binding protein (CREB)-binding protein (CBP), and it increases the transactivation function of CBP. The phosphoenolpyruvate carboxykinase (PEPCK) promoter was used as a model system to explore the role of SRCAP in the regulation of transcription mediated by factors that utilize CBP as a coactivator. We show that transcription of a PEPCK chloramphenicol acetyltransferase (CAT) reporter gene activated by protein kinase A (PKA) is enhanced 7-fold by SRCAP. In the absence of PKA this SRCAP-mediated enhancement does not occur, suggesting that SRCAP functions as a coactivator for PKA-activated factors such as CREB. Replacing the PEPCK promoter binding site for CREB with a binding site for Gal4 (⌬CRE (cAMP-responsive element) Gal4 PEPCK-CAT reporter gene) blocks the ability of SRCAP to activate transcription despite the presence of PKA. Expression of a Gal-CREB chimera restores the ability of PKA to regulate transcription of the ⌬CRE Gal4 PEPCK gene and restored the ability of SRCAP to stimulate PKAactivated transcription. In addition, SRCAP in the presence of PKA enhances the ability of the Gal-CREB chimera to activate transcription of a Gal-CAT reporter gene that contains only binding sites for Gal4. SRCAP binds to CBP amino acids 280 -460, a region that is important for CBP to function as a coactivator for CREB. Overexpression of a SRCAP peptide corresponding to this CBP binding domain acts as a dominant negative inhibitor of CREB-mediated transcription. Structurefunction studies were done to explore the mechanism(s) by which SRCAP regulates transcription. These studies indicate that the N-terminal region of SRCAP, which contains five of the seven regions that comprise the ATPase domain, is not needed for activation of CREBmediated transcription. SRCAP apparently has several domains that participate in the activation of transcription.The transcription factor cAMP-responsive element-binding protein (CREB) 1 regulates the transcription of a number of genes (for review, see Refs. 1 and 2). It stimulates a low level of basal transcription, which has been proposed to be mediated through action of CREB domains that bind directly to TAF 110, TAF 130, TFIIB and TBP (3-7). CREB also stimulates a much higher level of transcription when it is activated in response to diverse biological stimuli such as neural and hormonal signals. These signals stimulate phosphorylation of CREB within the kinase-inducible domain. Phosphorylation of serine 133 within the kinase-inducible domain by several kinases, including calmodulin kinase II and IV, protein kinase A, ribosomal S6 kinase 1-3, mitogen-and stress-activated protein kinase 1, and mitogen-activated protein kinase-activated protein kinase 2/3, leads to the activation of transcription (for review, see Ref. 8). Although phosphorylation o...

Larval zebrafish as a model for glucose metabolism: expression of phosphoenolpyruvate carboxykinase as a marker for exposure to anti-diabetic compounds

“…Glucagon activates the expression of PEPCK through the activation of cAMP leading to increased binding to cAMP elements in the PEPCK promoter (Leahy et al 1999, Yamada et al 1999, Herzig et al 2001, Liu et al 2001, Monroy et al 2001, Waltner-Law et al 2003. In addition, glucocorticoids, atRA, and thyroid hormone activate PEPCK gene expression (Stafford et al 2001, Waltner-Law et al 2003.…”

“…The mammalian PEPCK promoter region contains cis-acting elements that mediate activation by glucocorticoids, glucagon, thyroid hormone, and retinoic acid (Quinn & Granner 1990, Hall et al 2000, Monroy et al 2001, Waltner-Law et al 2003. It has been determined that the proximal promoter (K477 to K1 bp) contains the sequences required for positive regulation of PEPCK, and that this region also contains sequences that are necessary for glucose-mediated inhibition (Cournarie et al 1999).…”

“…Because PEPCK mRNA expression is transcriptionally modified by several glucoregulatory hormones, including insulin and glucagon, it is an excellent marker to investigate the effects of compounds on the regulation of glucose levels. Glucagon stimulates PEPCK through activation of cyclic AMP (Leahy et al 1999, Yamada et al 1999, Herzig et al 2001, Liu et al 2001, Monroy et al 2001, Waltner-Law et al 2003. In addition, PEPCK gene expression is also induced by glucocorticoids, all-trans retinoic acid, and thyroid hormone (Stafford et al 2001, Waltner-Law et al 2003, whereas both glucose and insulin inhibit PEPCK expression (O'Brien et al 2001).…”

Structural and Functional Conservation of the NuA4 Histone Acetyltransferase Complex from Yeast to Humans

“…This large protein is related to p400/hDomino over the SWI2 domain but lacks the SANT and HSA domains. It was shown to be involved in transcription regulation by CBP (27,36).…”

“…However, SRCAP does not contain HSA and SANT domains. SRCAP has been found previously to bind and cooperate with the CREB-binding protein (CBP) to activate transcription (27,36). YL-1 is a nuclear protein that is able to FIG.…”