1874
IST is not the RNA target ( TAR ) for Tat trans - activation ; however , because it relies entirely on cellular factors for activity , IST may serve to provide abundant RNA targets for Tat trans - activation without a requirement for full - length viral mRNA expression .
 IST, Tat, IST, Tat
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 IST, Tat, IST, Tat