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Title: Protein phosphatase inhibitors induce the sustained expression of the Egr-1 gene and the hyperphosphorylation of its gene product
Authors: Cao, X. 
Mahendran, R. 
Guy, G.R. 
Tan, Y.H.
Issue Date: 25-Jun-1992
Citation: Cao, X., Mahendran, R., Guy, G.R., Tan, Y.H. (1992-06-25). Protein phosphatase inhibitors induce the sustained expression of the Egr-1 gene and the hyperphosphorylation of its gene product. Journal of Biological Chemistry 267 (18) : 12991-12997. ScholarBank@NUS Repository.
Abstract: The immediate-early gene Egr-1 is strongly and rapidly induced in human and mouse Balb/c fibroblasts by okadaic acid and calyculin A, both specific inhibitors of protein serine/threonine phosphatases 1 and 2A. In contrast to the transient induction of the Egr-1 gene by serum or phorbol 12-myristate 13-acetate, these phosphatase inhibitors stimulated a sustained induction of the Egr-1 gene. The induction is shown to occur transcriptionally and is sustained post- transcriptionally. Okadaic acid-induced Egr-1 mRNA is significantly more stable than serum-induced Egr-1 mRNA. The half-life of serum-induced Egr-1 mRNA is estimated to be 12 min, compared with a half life of 2 h for okadaic acid-induced Egr-1 mRNA. Okadaic acid also induced the expression of the related immediateearly genes Egr-2 and Egr-3 albeit to a lesser extent than Egr-1. Treatment of cells with okadaic acid and calyculin A also induced the synthesis of Egr-1 protein. The Egr-1 protein is weakly or not phosphorylated in quiescent cells, but multiple species of the phosphorylated forms of the Egr-1 protein are detected in cells treated with either of the phosphatase inhibitors. Simultaneous treatment of cells with TPA and okadaic acid synergistically induced Egr-1 gene expression, and H7 strongly inhibits this induction. Taken together, the results indicate that the induction of Egr-1 gene transcription and the phosphorylation of the induced Egr-1 protein are under the control of protein kinase(s) and protein phosphatase(s). The phosphorylation and dephosphorylation of Egr-1 protein may play a role in controlling cell growth.
Source Title: Journal of Biological Chemistry
ISSN: 00219258
Appears in Collections:Staff Publications

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