13838
We have previously demonstrated that a mutated form of the human CIITA gene , coding for a protein lacking the amino terminal 151 amino acids , acts as a potent dominant-negative suppressor of HLA class II expression .
 ( protein: HLA class II, None) , ( DNA: human CIITA gene, None) , ( protein: CIITA, None) , ( protein: amino terminal 151 amino acids, 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: HLA class II, None) , ( DNA: human CIITA gene, None) , ( protein: CIITA, None) , ( protein: amino terminal 151 amino acids, None) 