7570
Smad6 and Smad7 prevent ligand-induced activation of signal-transducing Smad proteins in the transforming growth factor-beta family .
 ( protein: transforming growth factor-beta family, None) , ( protein: signal-transducing Smad proteins, None) , ( protein: Smad6, None) , ( protein: Smad7, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: transforming growth factor-beta family, None) , ( protein: signal-transducing Smad proteins, None) , ( protein: Smad6, None) , ( protein: Smad7, None) 