title: A novel intronic promoter of the Crem gene induces small ICER (smICER) isoforms.
abstract: The transcription factors cAMP-responsive element binding protein (CREB) and cAMP-responsive element modulator (CREM) regulate gene transcription in response to elevated cAMP levels. The Crem isoform inducible cAMP early repressor (Icer) is transcribed by the internal promoter P2 as a critical regulator of multiple cellular processes. Here, we describe a novel inducible Crem isoform, small Icer (smIcer), regulated by a newly identified promoter (P6). ChIP revealed binding of CREB to P6 in human and mouse myocardium. P6 activity was induced by constitutively active CREB or stimulation of adenylyl cyclase. In mice, smIcer mRNA was ubiquitously expressed and transiently induced by β-adrenoceptor stimulation e.g., in heart and lung. SmICER repressed both basal and cAMP-induced activities of P6 and P2 promoters. Stimulation of adenylyl cyclase induced P2 and P6 in cell type-specific manner. Alternative translational start sites resulted in three different smICER proteins, linked to increased apoptosis sensitivity. In conclusion, the Crem gene provides two distinct and mutually controlled mechanisms of a cAMP-dependent induction of transcriptional repressors. Our results suggest not only that smICER is a novel regulator of cAMP-mediated gene regulation, but also emphasize that biological effects that have been ascribed solely to ICER, should be revised with regard to smICER.
authors.affiliation: 2Institute of Pharmacology and Toxicology, University of Münster, Domagkstr. 12, 48149 Münster, Germany. seidl@uni-muenster.de.
authors.forename: Matthias D
authors.initials: MD
authors.lastname: Seidl
authors.forename: Frank
authors.initials: F
authors.lastname: Nunes
authors.forename: Benedikt
authors.initials: B
authors.lastname: Fels
authors.forename: Iris
authors.initials: I
authors.lastname: Hildebrandt
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Schmitz
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulze-Osthoff
authors.forename: Frank U
authors.initials: FU
authors.lastname: Müller
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D051786:Cyclic AMP Response Element Modulator / Q000235:genetics / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C497410:CREM protein, human; C497411:Crem protein, mouse; D051786:Cyclic AMP Response Element Modulator; D000242:Cyclic AMP
keywords: CREB; apoptosis; cAMP; cyclic AMP; gene regulation; transcription factors