Fig. 3

The activity of CDK9, but not CDK2, is required for H1.4-S187 phosphorylation. a Pluripotent NT2 cells were treated for increasing intervals with 10 µM NU6140 or 1 µM flavopiridol to preferentially inhibit CDK2 and CDK9, respectively. The global abundance of pS18-H1.5 and pS187-H1.4 was assessed by immunoblotting whole-cell lysates. The blot for histone H3 serves as a loading control. The 0 h time points provide a solvent control (DMSO). Commercial antisera (Active Motif) was used to detect pS18-H1.5. b HeLa cells were treated with DMSO or 10 μM NU6140 for 1 h. The loss of CDK2-mediated phosphorylation of CDK7-T170 [50] was assessed by immunoblotting whole-cell lysates with the indicated antisera. c HeLa cells were treated with DMSO or 1 μM flavopiridol for 1 h. Altered phosphorylation in the CTD heptad repeats of RNAP II [51] was assessed by immunoblotting whole-cell lysates with the indicated antisera. The numbers below each panel indicate densitometry for the treated samples relative to the respective control sample