The Pim-1 kinase regulates HBP1 expression.
A, exogenous Pim-1 regulates HBP1 expression. The protein levels of Pim-1 and HBP1 were measured by Western blotting in HeLa, U2OS, and 2BS cells transfected with either pITA-FLAG-Pim-1 or pITA (as a control) (top). The mRNA levels of HBP1 were measured by real-time PCR (bottom). B, endogenous Pim-1 regulates HBP1 expression. The protein levels of Pim-1 and HBP1 were measured by Western blotting in HeLa, U2OS, and 2BS cells transfected with pLL3.7-shPim-1-1, pLL3.7-shPim-1-2, or pLL3.7 (as a control) (top). The mRNA levels of HBP1 were measured by real-time PCR (bottom). C, Pim-1 prolongs the half-life of HBP1. HeLa cells were stably transfected with pITA, pITA-FLAG-Pim-1, pLL3.7, or pLL3.7-shPim-1 through lentiviral infection, respectively. Cells were incubated with the protein translation inhibitor CHX for 0, 30, 60, or 90 min before harvest. Pim-1 and HBP1 protein levels were detected by Western blotting. GAPDH was used as the loading control (top). Quantification of HBP1 protein levels was determined using TotalLab software and normalized to GAPDH, and densitometry was plotted for the mean ± S.D. (error bars) of three independent experiments (bottom). Error bars represent S.D.