Amino Acids Control Mammalian Gene Transcription: Activating Transcription Factor 2 Is Essential for the Amino Acid Responsiveness of the CHOP Promoter

Abstract

In mammals, plasma concentration of amino acids is affected by nutritional or pathological conditions. It has been well established that nutrients, and particularly amino acids, are involved in the control of gene expression. Here we examined the molecular mechanisms involved in the regulation of CHOP (a CCAAT/enhancer-binding protein [C/EBP]-related gene) expression upon amino acid limitation. We have previously shown that regulation of CHOP mRNA expression by amino acid concentration has both transcriptional and posttranscriptional components. We report the analysis of cis- and trans-acting elements involved in the transcriptional activation of the human CHOPgene by leucine starvation. Using a transient expression assay, we show that a cis-positive element is essential for amino acid regulation of the CHOP promoter. This sequence is the first described that can regulate a basal promoter in response to starvation for several individual amino acids and therefore can be called an amino acid response element (AARE). In addition, we show that the CHOP AARE is related to C/EBP and ATF/CRE binding sites and binds in vitro the activating transcription factor 2 (ATF-2) in starved and unstarved conditions. Using ATF-2-deficient mouse embryonic fibroblasts and an ATF-2-dominant negative mutant, we demonstrate that expression of this transcription factor is essential for the transcriptional activation of CHOP by leucine starvation. Altogether, these results suggest that ATF-2 may be a member of a cascade of molecular events by which the cellular concentration of amino acids can regulate mammalian gene expression.

ACKNOWLEDGMENTS

We are grateful to S. Ishii for the ATF-2 and ATF-2Ala expression plasmids and to U. Schiebler for providing anti-C/EBPβ serum. We thank V. Poli and D. Ron for the gift of the C/EBPβ-deficient MEF. We also thank D. Ron for the anti-ATF-4 serum.

This work was supported by grants from the Institut National de la Recherche Agronomique, the Fondation pour la Recherche Médicale, and the Arthritis Foundation (A.M.R.). C. Jousse is a recipient of a French M.E.N.S.R. predoctoral scholarship and a DANONE research scholarship.