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The HTLV-I LTR contains three conserved regulatory elements known as 21 base pair repeats which are required for stimulation of gene expression by the transactivator protein tax .
 DNA: HTLV-I LTR; DNA: 21 base pair repeats; DNA: regulatory elements; protein: transactivator protein; protein: tax
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: HTLV-I LTR; DNA: 21 base pair repeats; DNA: regulatory elements; protein: transactivator protein; protein: tax