Inhibition of protein phosphatases activates P4 promoter of the human insulin-like growth factor II gene through the specific promoter element.
To understand the transcriptional regulation of the human insulin-like growth factor II (IGF-II) gene, we examined the effects of okadaic acid, a potent in vitro inhibitor of protein phosphatases, on the activation of human IGF-II gene expression. Treatment of A-549 human lung adenocarcinoma cells with okadaic acid increased expression of the IGF-II mRNAs. Since the 4.8-kb mRNA is transcribed under the control of human IGF-II P4 promoter, we examined the P4 promoter element responsible for the okadaic acid-mediated transcriptional activation. Transfection of IGF-II P4 promoter-chloramphenicol acetyltransferase constructs demonstrated that the effects of okadaic acid on the induction of IGF-II gene expression are mediated through multiple promoter elements, including an Egr-1 consensus element. We have also shown that okadaic acid induced the expression of the transcription factor Egr-1. Moreover, by using a GAL4-Egr-1 fusion protein, we have directly demonstrated that okadaic acid positively regulates Egr-1 transcriptional activity in vivo. These results indicate that protein phosphatases play an important role in the transcriptional regulation of the IGF-II.
Hyun
S W
SW
Laboratory of Molecular Genetics, Korea Institute of Science and Technology, Daejon.
Park
K
K
Lee
Y S
YS
Lee
Y I
YI
Kim
S J
SJ
D000230:Adenocarcinoma; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004247:DNA; D004268:DNA-Binding Proteins / Q000235:genetics; D051766:Early Growth Response Protein 1; D004988:Ethers, Cyclic / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008175:Lung Neoplasms; D008969:Molecular Sequence Data; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D004988:Ethers, Cyclic; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D019319:Okadaic Acid; D007335:Insulin-Like Growth Factor II; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D010749:Phosphoprotein Phosphatases