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Retinoblastoma protein ( RB ) is a tumor suppressor and functions as a transcriptional repressor by binding and inactivating the transactivator E2F-I .
 ( protein: transcriptional repressor, None) , ( DNA: transactivator E2F-I, None) , ( protein: RB, None) , ( protein: Retinoblastoma protein, 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: transcriptional repressor, None) , ( DNA: transactivator E2F-I, None) , ( protein: RB, None) , ( protein: Retinoblastoma protein, None) 