Ets1 is an effector of the transforming growth factor β (TGF-β) signaling pathway and an antagonist of the profibrotic effects of TGF-β

Extracellular matrix (ECM) production and turnover are tightly controlled under normal physiological conditions. Ets factors regulate matrix turnover by activating transcription of several metalloproteinases (MMPs) and are frequently overexpressed in aggressive tumors and arthritis. Because of the prominent role of transforming growth factor beta (TGF-beta) in ECM synthesis, this study was undertaken to determine the possible interactions between Ets1 and the TGF-beta pathway. Experiments using adenoviral delivery of Ets1 in human fibroblasts have established that Ets1 strongly suppresses TGF-beta induction of collagen type I and other matrix-related genes and reverses TGF-beta-dependent inhibition of MMP-1. Subsequent experiments utilizing COLIA2 promoter demonstrated that Ets1 in the presence of TGF-beta signaling interferes with the stimulatory role of p300. To gain further insight into the mechanism of Ets1 inhibition of the TGF-beta signaling, the protein levels and post-translational modifications of Ets1 after TGF-beta treatment were analyzed. The level of total Ets1 protein was not affected after 24 h of TGF-beta stimulation. Moreover, TGF-beta did not affect either serine or threonine phosphorylation levels of Ets1. However, TGF-beta induced rapid and prolonged lysine acetylation of Ets1. In addition, analyses of endogenous p300-Ets1 complexes revealed that acetylated Ets1 is preferentially associated with the p3oo/CBP complexes. TGF-beta treatment leads to dissociation of Ets1 from the CBP/p300 complexes. Together, these findings suggest that elevated expression of Ets1 in fibroblasts fundamentally alters their responses to TGF-beta in favor of matrix degradation and away from matrix deposition as exemplified by arthritis and cancer.