Induction of CHOP expression by amino acid limitation requires both ATF4 expression and ATF2 phosphorylation.
The CHOP gene is transcriptionally induced by amino acid starvation. We have previously identified a genomic cis-acting element (amino acid response element (AARE)) involved in the transcriptional activation of the human CHOP gene by leucine starvation and shown that it binds the activating transcription factor 2 (ATF2). The present study was designed to identify other transcription factors capable of binding to the CHOP AARE and to establish their role with regard to induction of the gene by amino acid deprivation. Electrophoretic mobility shift assay and transient transfection experiments show that several transcription factors that belong to the C/EBP or ATF families bind the AARE sequence and activate transcription. Among all these transcription factors, only ATF4 and ATF2 are involved in the amino acid control of CHOP expression. We show that inhibition of ATF2 or ATF4 expression impairs the transcriptional activation of CHOP by amino acid starvation. The transacting capacity of ATF4 depends on its expression level and that of ATF2 on its phosphorylation state. In response to leucine starvation, ATF4 expression and ATF2 phosphorylation are increased. However, induction of ATF4 expression by the endoplasmic reticulum stress pathway does not fully activate the AARE-dependent transcription. Taken together our results demonstrate that at least two pathways, one leading to ATF4 induction and one leading to ATF2 phosphorylation, are necessary to induce CHOP expression by amino acid starvation. This work was extended to the regulation of other amino acid regulated genes and suggests that ATF4 and ATF2 are key components of the amino acid control of gene expression.
Averous
Julien
J
Unité de Nutrition et Métabolisme Protéique, Institut National de la Recherche Agronomique de Theix, 63122 Saint Genès Champanelle, France.
Bruhat
Alain
A
Jousse
Céline
C
Carraro
Valérie
V
Thiel
Gerald
G
Fafournoux
Pierre
P
D051698:Activating Transcription Factor 2; D051701:Activating Transcription Factor 4; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007930:Leucine / Q000737:chemistry; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D009841:Oligonucleotides / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
C497105:ATF2 protein, human; C497109:ATF4 protein, human; D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D022762:CCAAT-Enhancer-Binding Proteins; D017362:Cyclic AMP Response Element-Binding Protein; C497249:DDIT3 protein, human; C497250:Ddit3 protein, mouse; D009841:Oligonucleotides; D034741:RNA, Small Interfering; D014157:Transcription Factors; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP; D004247:DNA; D008156:Luciferases; D007930:Leucine