Regulation of the human CHOP gene promoter by the stress response transcription factor ATF5 via the AARE1 site in human hepatoma HepG2 cells.
OBJECTIVE
Activating transcription factor (ATF) 5 is a member of the cAMP response element-binding protein (CREB)/ATF family of transcription factors. We have shown that ATF5 is a stress response transcription factor that responds to amino acid limitation, arsenite exposure, or cadmium exposure. In this study we investigated whether ATF5 is involved in the regulation of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) gene expression.


METHODS
We used a transient transfection system to express ATF5 and analyzed the regulation of CHOP gene promoter in human hepatoma, HepG2 cells. We also studied the effect of ATF5 knockdown on arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.


RESULTS
We showed that ATF5 activates the CHOP gene promoter in HepG2 cells. Both deletion analysis and point mutations of the promoter revealed that amino acid response element (AARE) 1 is responsible for ATF5-dependent promoter activation. Furthermore, the existence of either AARE1 or activating protein-1 (AP-1) site is sufficient for transcriptional activation of the CHOP gene promoter by arsenite exposure, although complete induction requires the existence of both elements. We also demonstrated that knockdown of ATF5 reduced arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.


CONCLUSIONS
These results suggested that the CHOP gene is a potential target for ATF5, and that ATF5 raises the arsenite-induced CHOP gene expression level via the AARE1 site in HepG2 cells.
Yamazaki
Takashi
T
The Laboratory of Environmental Molecular Physiology, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan.
Ohmi
Asako
A
Kurumaya
Haruka
H
Kato
Kenji
K
Abe
Takanori
T
Yamamoto
Hiroyuki
H
Nakanishi
Noriko
N
Okuyama
Ryuichi
R
Umemura
Mariko
M
Kaise
Toshikazu
T
Watanabe
Ryuya
R
Okawa
Yoshiko
Y
Takahashi
Shigeru
S
Takahashi
Yuji
Y
D051696:Activating Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D000596:Amino Acids / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D018053:Arsenites / Q000494:pharmacology; D001665:Binding Sites; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics; D010957:Plasmids; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000494:pharmacology; D020218:Response Elements / Q000235:genetics*; D017670:Sodium Compounds / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000235:genetics; D051742:Transcription Factor CHOP / Q000235:genetics*; D014162:Transfection; D015854:Up-Regulation
C507532:ATF5 protein, human; D051696:Activating Transcription Factors; D000596:Amino Acids; D018053:Arsenites; C497249:DDIT3 protein, human; D034741:RNA, Small Interfering; D017670:Sodium Compounds; D018808:Transcription Factor AP-1; D051742:Transcription Factor CHOP; C017947:sodium arsenite; D008156:Luciferases