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Recently, transcription factors known as STATs ( signal transducers and activators of transcription ) have been shown to be tyrosine phosphorylated and activated in response to a number of cytokines that bind hematopoietin receptors and activate JAK kinases .
 ( protein: signal transducers and activators of transcription, None) , ( protein: transcription factors, None) , ( protein: STATs, None) , ( protein: cytokines, None) , ( protein: hematopoietin receptors, None) , ( protein: JAK kinases, 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: transcription factors, None) , ( protein: STATs, None) , ( protein: cytokines, None) , ( protein: hematopoietin receptors, None) , ( protein: JAK kinases, None) 