A tripartite array of transcription factor binding sites mediates cAMP induction of phosphoenolpyruvate carboxykinase gene transcription and its inhibition by insulin.
Transcription of the phosphoenolpyruvate carboxykinase (PEPCK) gene is induced upon activation of protein kinase A by cAMP and phosphorylation of Ser-133 in the transcription factor, cAMP-response element binding protein (CREB), and this induction is inhibited by insulin. We show here that insulin does not act by dephosphorylating CREB or by affecting heterologous kinases that phosphorylate Ser-129 or Ser-142 in CREB. In addition, insulin inhibition of minimal PEPCK promoter activity induced by CREB-GAL4 + protein kinase A was equivalent to inhibition of basal transcription, and thus cAMP-independent. On the other hand, nearly complete insulin inhibition is observed with the full PEPCK promoter (-600/+69), indicating that other factors are involved. The additional promoter elements required for induction by protein kinase A lie within -271 nucleotides of the start site and correspond to putative binding sites for activator protein-1 and CAAT/enhancer-binding protein (C/EBP), first identified by Roesler et al. (Roesler, W. J., McFie, P. J., and Puttick, D. M., (1993) J. Biol. Chem. 268, 3791-3796). This tripartite array of binding sites for CREB, C/EBP, and activator protein-1 (AP-1) factors forms a cAMP response unit that, together with the minimal promoter, can mediate both induction by cAMP and inhibition by insulin. Thus, for the PEPCK gene with a single CREB site, the CREB.CBP.RNA polymerase II complex cannot mediate either induction by cAMP or inhibition by insulin.
Yeagley
D
D
Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Agati
J M
JM
Quinn
P G
PG
D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004790:Enzyme Induction / Q000235:genetics; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000378:metabolism; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000096:biosynthesis / Q000235:genetics*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
D022762:CCAAT-Enhancer-Binding Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D007328:Insulin; D009687:Nuclear Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019764:Phosphoenolpyruvate Carboxykinase (ATP)