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 (PEPCH) gene is induced upon activation of protein kinase A by cAMP and phosphorylati on of Ser-133 in the transcription factor, cAMP-response element bindi ng protein (CREB), and this induction is inhibited by insulin, We show here that insulin does not act by dephosphorylating CREB or by affect ing heterologous kinases that phosphorylate Ser-129 or Ser-142 in CREB , In addition, insulin inhibition of minimal PEPCK promoter activity i nduced by CREB-GAL4 + protein kinase A was equivalent to inhibition of basal transcription, and thus cAMP-independent. On the other hand, ne arly complete insulin inhibition is observed with the full PEPCK promo ter (-600/+69), indicating that other factors are involved, The additi onal promoter elements required for induction by protein kinase A lie within -271 nucleotides of the start site and correspond to putative b inding 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 prote in-1 (AP-1) factors forms a cAMP response unit that, together with the minimal promoter, can mediate both induction by cAMP and inhibition b y insulin, Thus, for the PEPCH gene with a single CREB site, the CREB. CBP.RNA polymerase II complex cannot mediate either induction by cAMP or inhibition by insulin.