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Suppression of Egr‐1 transcription through targeting of the serum response factor by oncogenic H‐Ras
Author(s) -
Shin Soon Young,
Bahk Young Yil,
Ko Jesang,
Chung IlYup,
Lee Young Seek,
Downward Julian,
Eibel Hermann,
Sharma Prem M,
Olefsky Jerrold M,
Kim YoungHo,
Lee Bonghee,
Lee Young Han
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600987
Subject(s) - biology , transcription factor , serum response factor , cancer research , serum response element , microbiology and biotechnology , genetics , gene
The transcription factor Egr‐1 functions as a key regulator in cellular growth, differentiation, and apoptosis. The loss of Egr‐1 expression is closely associated with tumor development, although the molecular mechanism behind the suppression of Egr‐1 is largely unknown. In this report, we show that growth factor‐induced transcriptional activation of Egr‐1 gene is downregulated by chronic expression of oncogenic H‐Ras in NIH3T3 fibroblasts. Our results demonstrate that phosphoinositide 3‐kinase (PI3K) signaling is necessary for oncogenic H‐Ras‐mediated reduction of Egr‐1 gene expression. Aberrant activation of PI3K signaling by oncogenic Ras decreased the level of serum response factor (SRF) protein through the acceleration of proteolysis, which resulted in decreased SRF binding to the serum response element (SRE) sites within the Egr‐1 promoter, leading to the suppression of Egr‐1 transcription. Inhibition of PI3K signaling restored the downregulation of SRF and Egr‐1 expression caused by oncogenic Ras. Our findings suggest a novel signaling mechanism by which prolonged activation of oncogenic H‐Ras can trigger the loss of tumor suppressor Egr‐1 through the PI3K pathway in NIH3T3 fibroblast model cell lines.