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The main activity of the silencer has been mapped to the first 900 bp of 5' flanking DNA , which contains nine binding sites for a nuclear factor present in non- erythroid cells but not in erythroid cells .
 DNA: 5' flanking DNA; cell type: erythroid cells; protein: nuclear factor; cell type: erythroid cells; DNA: silencer
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: 5' flanking DNA; cell type: erythroid cells; protein: nuclear factor; cell type: erythroid cells; DNA: silencer