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Protease treatment of nuclear extracts distinguishes between class II MHC X1 box DNA-binding proteins in wild-type and class II-deficient B cells .
 class II MHC X1 box DNA-binding proteins
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 class II MHC X1 box DNA-binding proteins