1240
Transcriptional activation by the HIV - 1 Tat protein requires specific residues in the hexanucleotide loop and trinucleotide bulge of the TAR RNA stem - loop structure found in the 5 ' - untranslated leader of all viral transcripts .
 HIV - 1 Tat protein, TAR
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 HIV - 1 Tat protein, TAR