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The IE2 gene product of human cytomegalovirus ( HCMV ) is one of a few viral regulatory proteins expressed immediately upon infection of the host cell .
 ( protein: IE2 gene product, None) , ( cell type: host cell, None) , ( protein: viral regulatory proteins, 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: IE2 gene product, None) , ( cell type: host cell, None) , ( protein: viral regulatory proteins, None) 