Inhibits CKII (IC50 range of 4-10 µM), Cdk7 (IC50 = ~20 µM), Cdk8 (IC50 = ~20 µM), and Cdk9 (IC50 = 3 µM); inhibits elongation during RNA polymerase II transcription; triggers p53-dependent apoptosis of human colon adenocarcinoma cells; inhibits trans-activated transcription of the Tat protein of HIV-1 (IC50 = ~4 µM).