424
We have found that the HTLV-1 transactivator protein , tax , acts as a costimulatory signal for GM-CSF and IL-2 gene transcription , in that it can cooperate with TCR signals to mediate high level gene expression .
 ( protein: tax, None) , ( protein: HTLV-1 transactivator protein, None) , ( protein: TCR, 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: tax, None) , ( protein: HTLV-1 transactivator protein, None) , ( protein: TCR, None) 