BMS-345541 inhibition of IKKβ in HTLV-1 infected cell. A) BMS-345541 reduced IKKβ activity in C8166 cells. Equal amount (1 mg) of cytoplasmic proteins was immunoprecipitated with anti-IKKβ antibody and mixed with 1 μM BMS-345541. The IKKβ activities were examined by in vitro kinase assay using GST-IκBα as a substrate. The [γ-32P]-labeled IκB-α protein was visualized by autoradiography. The IKKβ activities were quantitated by ImageQuant software. The bottom panel shows a commassie blue staining of GST-IκBα to show equal amount of substrate in each reaction. B) BMS-345541 inhibited IKKβ activity in C8166 cells in dose-dependent manner; however, Purvalanol A had no effect on IKKβ. Kinase assay were performed as described above using 0.01, 0.1, and 1 μM of BMS-345541 and 1, 10 μM of Purvalanol A. The stained gel below is a representative of the kinase reaction.