tokens: 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 .
folded_tokens: 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 .
labels: O O O O O B-protein_molecule O O B-protein_complex I-protein_complex O O B-other_name O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O B-DNA_domain_or_region O O O O O O O O O O O O O O O O O O O B-other_name I-other_name O B-cell_type I-cell_type I-cell_type O B-protein_molecule O O O