Figure 6.

The phosphorylated form of KLF8 acts as a mask to protect the overall stability of KLF8 protein. A, B. The phosphorylated form of KLF8 protein degrades to protect the unphosphorylated form. The MCF7-K8 and MCF7-K8-S48 cells were subjected to CHX chase assay as described above. The upper and lower bands of the wild-type KLF8 were quantified separately and compared to total expression of the wild-type KLF8 as well as the S48A mutant protein. C, D. The lifespan of the unphosphorylated form of KLF8 protein decreases in the absence of the phosphorylated form. The CHX chase assay was carried out similarly except that the MCF7-K8 cells were treated with the MEK inhibitor U0126 inhibitor before and during the chase assay as described in the Experimental Procedures.