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The normal cell cycle is regulated by several molecules, such as the tumor-suppressor protein pRb , the G1 cyclins , the cyclin-dependent kinases , and their inhibitors .
 ( protein: pRb, None) , ( protein: G1 cyclins, None) , ( protein: tumor-suppressor protein pRb, None) , ( protein: cyclin-dependent 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: pRb, None) , ( protein: G1 cyclins, None) , ( protein: tumor-suppressor protein pRb, None) , ( protein: cyclin-dependent kinases, None) 