2.2. In vitro kinase assay

c‐Jun (400 ng), ERK1 (200 ng), and histone H3.3 (200 ng) were used as substrates for in vitro kinase assays with 200 ng of active TOPK, MEK1, https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=1936 and https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=1937&familyId=557&familyType=ENZYME. Reactions were conducted at 30°C for 30 min in 1× kinase buffer (25‐mM Tris–HCl, pH 7.5, 5‐mM β‐glycerophosphate, 2‐mM DTT, 0.1‐mM Na₃VO₄, 10‐mM MgCl₂, and 5‐mM MnCl₂) containing 200‐μM ATP. The reactions were stopped, and the proteins were detected by western blotting.