Inhibitory effects of luteolin on VRK1 kinase activity.

<p>(A) and (B), <i>in vitro</i> kinase activity measurements for VRK1 with BAF (A) or VRK1 with histone H3 (B) were performed by increasing concentrations of luteolin (0.0, 1.0, 10, 50, 100, and 250 µM), and then VRK1 and substrate proteins were stained with silver nitrate. (C), Chemical structures and molecular weights of luteolin, eupatilin, and wogonin. (D) and (E), <i>in vitro</i> kinase assay for VRK1 with BAF were performed by increasing concentrations (0.0, 1.0, 10, 50, 100, and 250 µM) of eupatilin (D) or wogonin (E), and then VRK1 and BAF proteins were stained with silver nitrate. (F) and (G), Quantification of VRK1 auto-phosphorylation (F) or BAF phosphorylation (G) described in (B), (D) and (E). Data in (F) and (G) represent means of three independent experiments ±SEMs.