AN ANALYSIS OF REGULATORY ELEMENTS IN THE PHOSPHOENOLPYRUVATE CARBOXYKINASE (GTP) GENE WHICH ARE RESPONSIBLE FOR ITS TISSUE-SPECIFIC EXPRESSION AND METABOLIC CONTROL IN TRANSGENIC MICE

Sequences in the gene for P-enolpyruvate carboxykinase (PEPCK) which a re responsible for its complex pattern of transcriptional control were determined using transgenic mice containing a chimeric PEPCK-bovine g rowth hormone (bGH) gene consisting of a segment of the PEPCK promoter from -460 to +73, with mutations in specific regulatory domains. A mu tation in the cAMP response element (CRE) (-87 to -74), which binds CC ATT/enhancer-binding protein beta (C/EBP beta) and/or cAMP response el ement-binding protein (CREE), resulted in a 4- and 20-fold elevation i n the level of bGH mRNA in the liver and kidney of transgenic mice, re spectively. Expression of the PEPCK bGH gene in the liver was reduced 60% by a mutation in the P3 (I) region (-248 to -230), whereas express ion in the kidney was increased 10-fold by the same mutation. A mutati on in the P2 region (-200 to -164) greatly reduced expression of the P EPCK-bGH gene in the kidney but not in the liver Induction of hepatic PEPCK-bGH gene expression by Bt(2)cAMP was eliminated by mutations in the CRE, P1, P3(I), or by a double mutation of the CRE and P3(I). Muta tions in the CRE or P3(I) regions of the PEPCK promoter did not interf ere with the expected induction of the PEPCK-bGH gene in the liver at birth. None of the mutations in the PEPCK promoter interfered with the induction of transcription of the PEPCK-bGH gene in the liver when mi ce were fed a carbohydrate free diet or the deinduction of transcripti on from the PEPCK promoter caused by a diet high in carbohydrate, wher eas a mutation in P2 (an HNF-1 binding domain) eliminated dietary regu lation of transcription of the transgene in the kidney. A model to exp lain the role of the various elements in the PEPCK promoter on the con trol of PEPCK gene transcription in the liver and kidney is presented.