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We previously reported the purification of human PTF , a complex of four subunits , and the molecular cloning and characterization of PTF gamma and delta subunits .
 ( protein: human PTF, None) , ( protein: four subunits, 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: human PTF, None) , ( protein: four subunits, None) 