Casein kinase 2 (CK2) is required for the transforming growth factor (TGF)-β-induced microtubule acetylation on the soft matrix. (A, B) Mouse embryonic fibroblasts (MEFs) were seeded on fibronectin (10 μg/ml)-coated ∼0.5 kPa polyacrylamide gel (PAG) in a plastic culture dish with or without TGF-β (2 ng/ml), 4,5,6,7-tetrabromobenzotriazole (TBB) (10 μM), and blebbistatin (10 μM). After 8 h of incubation, protein lysates obtained from individual conditions were subjected to western blotting with the indicated antibodies. (C, D) Immunocytochemistry of MEFs seeded on fibronectin-coated ∼0.5 kPa PAG and coverslips with or without TGF-β (2 ng/ml) and TBB (10 μM) for 8 h. Graphs show the projected cell area of 30 cells randomly incubated on ∼0.5 kPa PAGs and coverslips. Statistical significance was determined via one-way analysis of variance (ANOVA) with Tukey’s post hoc test. Projected cell area; one-way ANOVA, F3,116 = 75.84. ***P < 0.005, n.s. not significant. Scale bar, 25 μm. For each value, measurements were made on 30 randomly photographed cells. (E) Wild-type (WT) and CK2α knockout (KO) MEFs were seeded on 0.5 kPa PAG in a plastic culture dish upon TGF-β stimulation for 8 h. (F) Measurement of projected cell area of WT and CK2α KO MEFs on ∼0.5 kPa PAGs (n = 30, each group). Statistical signifi-cance was determined via one-way ANOVA with Tukey’s post hoc test. Projected cell area; one-way ANOVA, F3,116 = 42.02. ***P < 0.005, n.s. not significant. For each value, measurements were made on 30 randomly photographed cells.