Amino acids control mammalian gene transcription: Activating transcriptionfactor 2 is essential for the amino acid responsiveness of the CHOP promoter

In mammals, plasma concentration of amino acids is affected by nutritional or pathological conditions. It has been well established that nutrients, an d particularly amino acids, are involved in the control of gene expression. Here we examined the molecular mechanisms involved in the regulation of CH OP (a CCAAT/enhancer-binding protein [C/EBP]-related gene) expression upon amino acid limitation, We have previously shown that regulation of CHOP mRN A expression by amino acid concentration has both transcriptional and postt ranscriptional components. We report the analysis of cis- and trans-acting elements involved in the transcriptional activation of the human CHOP gene by leucine starvation. Using a transient expression assay, rye show that a cis-positive element is essential for amino acid regulation of the CHOP pro moter. This sequence is the first described that can regulate a basal promo ter in response to starvation for several individual amino acids and theref ore can be called an amino acid response element (AARE). In addition, we sh ow that the CHOP AARE is related to C/EBP and ATF/CRE binding sites and bin ds in vitro the activating transcription factor 2 (ATF-2) in starved and un starved conditions. Using ATF-2-deficient mouse embryonic fibroblasts and a n ATF-2-dominant negative mutant, we demonstrate that expression of this tr anscription 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 concentrati on of amino acids can regulate mammalian gene expression.