passages.id: split_6_test_629_passage
passages.type: progene_text
passages.text: Formation of the RNA polymerase IIo* occurs only after transcription of templates carrying a functional TAR RNA element and is strongly inhibited by low concentrations of 5,6-dichloro-1-beta- D - ribofuranosyl benzimidazole ( DRB ) , a potent inhibitor of CDK9 , the protein kinase subunit of the Tat - associated kinase ( TAK ) .