764
Several studies have established that Tat releases an elongation block to the transcription of HIV long terminal repeat ( LTR ); however, it is not known whether this mechanism alone is sufficient to explain the block to HIV replication in human T cells when Tat is absent.
 ( DNA: LTR, None) , ( protein: elongation block, None) , ( DNA: HIV long terminal repeat, None) , ( protein: Tat, None) , ( cell type: human T cells, None) , ( protein: Tat, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( DNA: LTR, None) , ( protein: elongation block, None) , ( DNA: HIV long terminal repeat, None) , ( protein: Tat, None) , ( cell type: human T cells, None) , ( protein: Tat, None) 