Background:

5, 6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) is a transcriptional elongation inhibitor.

Cyclin-dependent kinases (CDKs) belong to a family of protein kinases involved in regulating the cell cycle, transcription, mRNA processing, and the differentiation of nerve cells.[1] They are expressed in all known eukaryotes. With cyclin, CDK shows kinase activity. CDKs are serine-threonine kinases [1].

DRB inhibited the activity of several carboxyl-terminal domain (CTD) kinases including casein kinase II, Cdk7, Cdk8, and Cdk9 with the IC50 of 4-10 μM,