Nuclear localization of proteasome subunit beta 5 serves as an independent prognostic biomarker and promotes invasion in colorectal cancer

Figure 4 Efficient knockdown of proteasome subunit beta 5 in colorectal cancer cells. A: PSMB5 mRNA levels. SW620 and SW480 cells were transfected with a PSMB5-targeting small interfering RNA (siRNA) pool or non-targeting control siRNA. PSMB5 mRNA was significantly reduced by PSMB5-targeting siRNA pool in both cell lines. Gene expression was normalized to GAPDH and is presented relative to non-targeting control siRNA (set as 1). Data are mean ± SD from three independent experiments. ^aP < 0.001 vs non-targeting control siRNA; B and C: PSMB5 protein levels. Whole-cell lysates were analyzed by Western blot (B) with quantitative analysis (C). GAPDH served as a loading control. Data are mean ± SD from three independent experiments. ^aP < 0.001 vs Scr; D: Subcellular distribution. Cytoplasmic and nuclear fractions from SW620 and SW480 cells transfected with PSMB5-targeting siRNA pool or non-targeting control siRNA were analyzed by western blot. Purity of fractions was confirmed using GAPDH (cytoplasmic marker) and Lamin B1 (nuclear marker). Scr: Non-targeting control small interfering RNA; sipool: Proteasome subunit beta 5-targeting small interfering RNA pool; PSMB5: Proteasome subunit beta 5; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; C: Cytoplasmic; N: Nuclear.