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The tax gene product of human T-cell leukemia virus type I ( HTLV-I ) is a potent transcriptional activator that both stimulates viral gene expression and activates an array of cellular genes involved in T-cell growth .
 transcriptional activator, T-cell, cellular genes
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:
 transcriptional activator, T-cell, cellular genes