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We show that a central core in the kappa E3' enhancer is active at the pre-B-cell stage but is repressed by flanking negative-acting elements .
 DNA: flanking negative-acting elements; DNA: kappa E3' enhancer
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:
 DNA: flanking negative-acting elements; DNA: kappa E3' enhancer