12878
Recent studies reveal that a family of transcription factors , signal transducers and activators of transcription ( STATs ) directly mediate many cytokine signals .
 ( protein: signal transducers and activators of transcription, None) , ( protein: cytokine, None) , ( protein: transcription factors, None) , ( protein: STATs, 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: signal transducers and activators of transcription, None) , ( protein: cytokine, None) , ( protein: transcription factors, None) , ( protein: STATs, None) 