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The activity of DNA relaxing enzymes (e.g. topoisomerases I and II ) in nuclear extracts was measured using a PBR 322-relaxation-assay .
 protein: DNA relaxing enzymes
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 protein: DNA relaxing enzymes