Fig. 6.

MSK2 binds to p300 and antagonizes its activity. (A) Human embryonic kidney (HEK) 293T cells were cotransfected with p300-HA and MSK2-V5 expression plasmids. After 48 hours, equal amounts of total protein were immunoprecipitated with V5 antibody. (B) Cells as in panel (A) were transfected with control or p300-HA plasmids. Endogenous MSK2 was immunoprecipitated with MSK2 antibody, and precipitates were immunoblotted with p300 antibody. (C) Endogenous MSK2-p300 complexes were detected in HEK 293T cells by immunoprecipitation with MSK2 antibody and Western blot analysis. (D) U2OS cells were cotransfected with GAL4-luc and p300-GAL4DBD plasmids in the presence of empty vector or MSK2, and luciferase activity was analyzed 48 hours later. Error bars represent SDM of four samples. The luciferase values are relative to the activity of GAL4-luc promoter in the presence of p300-GAL4DBD. Statistical analysis was performed by ANOVA and p value was calculated for the indicated comparison: *** P < 0.001. (E) U2OS cells were transfected with control or MSK2 siRNAs for 72 hours. Control cells were treated with the histone deacetylase inhibitor trichostatin A (TSA) for 16 hours. Amounts of p53 acetylated at Lys³⁸² (Ac-K382p53) and total p53 were analyzed by Western blot.