INDUCIBLE CAMP EARLY REPRESSOR CAN MODULATE TYROSINE-HYDROXYLASE GENE-EXPRESSION AFTER STIMULATION OF CAMP SYNTHESIS

Members of the CREB/CREM/ATF family of transcription factors either en hance or repress transcription after binding to the cAMP response elem ents (CREs) of numerous genes, The rat gene for tyrosine hydroxylase ( TH) bears a canonical CRE, at base pairs -38 through -45 from the tran scription initiation site, that is essential for basal and cAMP-stimul ated transcription (Kim, K.-S., Lee, M. K., Carroll, J., and Job, T.H. (1993) J. Biol. Chem, 268, 15689-15695; Lazaroff, M., Patankar, S., Y oon, S. O., and Chikaraishi, D. M. (1995) J. Biol. Chem. 270, 21579-21 589). The current study identifies CRE-binding proteins induced in pha rmacological paradigms characterized by TH activation. PC12- and rat a drenal gland-derived nuclear proteins retarded a TH-CRE oligonucleotid e in gel mobility shift assays with virtually identical patterns, Thes e differed substantially from patterns exhibited by extracts from locu s ceruleus or from neuroblastoma (SK-N-BE(2)C) and locus ceruleus-deri ved (CATH.a) cell lines, Forskolin stimulation of PC12 cells and reser pine treatment of rats increased, in nuclear extracts derived from cel ls and adrenal glands, respectively, the amount of a fast moving CRE/p rotein complex that was supershifted by an anti-CREM antibody, Subsequ ent Western, Northern, and polymerase chain reaction analyses indicate d that a specific member of the CREM family, the inducible cAMP early repressor (ICER), was strongly induced in both systems, Cotransfection of PC12 cells with TH2400CAT plasmid and the expression vector pCMV-I CER-Ib demonstrated that ICER efficiently represses the transcriptiona l activity of the TH gene promoter, In addition, PKA-stimulated transc riptional activity of the promoter was effectively suppressed by ICER. These results suggest that ICER can modulate cAMP-stimulated transcri ption of the TH gene and provide a model accounting for rapid reversal of increased TH transcription following elevations in cAMP.