Figure 3. Stability of the SSRP1 and SPT16 proteins is reduced when expression of mRNA is inhibited via RNAi.(A)Western blot analysis of SPT16, SSRP1, β-actin and p53 protein levels in HeLa cells transduced with shRNAs targeting SPT16, SSRP1 or GFP using cell lysates prepared at the indicated times after addition of 50 μg/ml cycloheximide (CHX). β-actin and p53 were evaluated as examples of proteins with long and short half-lives, respectively.(B)Quantitation of data shown in (A) corresponding to SPT16, and SSRP1 proteins normalized to the intensity of β-actin bands. Normalized intensities of bands at ‘time 0’ were set at 1.0.(C)Western blot analysis of SPT16, SSRP1, and β-actin protein levels in HeLa cells transfected with siRNA against GFP, SSRP1, or SPT16 and treated with 100 nM bortezomib (Btz) for 4 h.