Synergism between transcription factors TFE3 and Smad3 in transforming growth factor-beta-induced transcription of the Smad7 gene

Activation of transforming growth factor-beta (TGF-beta) receptors triggers phosphorylation of Smad2 and Smad3. After binding to Smad4, the complex en ters the nucleus and interacts with other transcription factors to activate gene transcription. Unlike other Smads, Smad7 inhibits phosphorylation of Smad2 and Smad3, and its transcription is induced by TGF-beta, suggesting a negative feedback loop. Here, we show that TFE3 and Smad3 synergistically mediate TGF-beta -induced transcription from the Smad7 promoter by binding to an E-box and two adjacent Smad binding elements (SBEs ), respectively. A precise 3-base pair spacer between one SEE and the E-box is essential. Pre viously, me showed that a similar arrangement between a SEE and an E-box of an element is essential for TGF-beta -dependent transcription of the plasm inogen activator inhibitor-1 gene (PAI-1) and that TGF-beta -induced phosph orylation of Smad3 triggers its association with TFE3. Thus, TFE3-Smad3 res ponse elements may represent a common target for TGF-beta -induced gene exp ression.