Distinct C/EBPalpha motifs regulate lipogenic and gluconeogenic gene expression in vivo.
The C/EBPalpha transcription factor regulates hepatic nitrogen, glucose, lipid and iron metabolism. However, how it is able to independently control these processes is not known. Here, we use mouse knock-in mutagenesis to identify C/EBPalpha domains that specifically regulate hepatic gluconeogenesis and lipogenesis. In vivo deletion of a proline-histidine rich domain (PHR), dephosphorylated at S193 by insulin signaling, dysregulated genes involved in the generation of acetyl-CoA and NADPH for triglyceride synthesis and led to increased hepatic lipogenesis. These promoters bound SREBP-1 as well as C/EBPalpha, and the PHR was required for C/EBPalpha-SREBP transcriptional synergy. In contrast, the highly conserved C/EBPalpha CR4 domain was found to undergo liver-specific dephosphorylation of residues T222 and T226 upon fasting, and alanine mutation of these residues upregulated the hepatic expression of the gluconeogenic G6Pase and PEPCK mRNAs, but not PGC-1alpha, leading to glucose intolerance. Our results show that pathway-specific metabolic regulation can be achieved through a single transcription factor containing context-sensitive regulatory domains, and indicate C/EBPalpha phosphorylation as a PGC-1alpha-independent mechanism for regulating hepatic gluconeogenesis.
Pedersen
Thomas A
TA
EMBL Mouse Biology Unit, Monterotondo, Italy.
Bereshchenko
Oxana
O
Garcia-Silva
Susana
S
Ermakova
Olga
O
Kurz
Elke
E
Mandrup
Susanne
S
Porse
Bo T
BT
Nerlov
Claus
C
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics* / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000235:genetics*; D005943:Gluconeogenesis / Q000235:genetics* / Q000502:physiology; D022781:Hepatocytes; D050155:Lipogenesis / Q000235:genetics* / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D051780:Sterol Regulatory Element Binding Protein 1 / Q000378:metabolism
D022763:CCAAT-Enhancer-Binding Protein-alpha; D017931:DNA Primers; C497388:Srebf1 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1