13621
Tax corresponds to a 40-kDa transforming protein from the pathogenic retrovirus human T-cell leukemia virus type 1 ( HTLV-1 ) that activates nuclear expression of the NF-kappaB /Rel family of transcription factors by an unknown mechanism .
 40-kDa transforming protein, NF-kappaB, NF-kappaB /Rel family, Tax, transcription factors
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:
 40-kDa transforming protein, NF-kappaB, NF-kappaB /Rel family, Tax, transcription factors