“…Cells were suspended in 50 μl of 5 mM Tris‐HCl, pH 7.4, containing 150 mM NaCl, 2 mM EDTA, 3 mM NaF, 0.5 mM dithiothreitol, 0.5 mM phenylmethylsulfonyl fluoride, disrupted by sonication (3×10 s, 0°C) and centrifuged (10 000× g , 10 min, 4°C). The supernatant was assayed for protein kinase activity using histone H1 as substrate [1].…”