FIGURE 7.

Expression of p16^INK4a or p19^ARF is recovered after exposure to arsenic in BALB/c 3T3 cells expressing knockdown PcG complexes. A, p16^INK4a or p19^ARF protein expression was recovered in knockdown BMI1 (left panel) or SUZ12 (right panel) stably infected BALB/c 3T3 cells after arsenic treatment. The proteins were prepared and subjected to Western blotting with specific primary antibodies and an HRP-conjugated secondary antibody. Detection of total β-actin was used to verify equal protein loading. B, the mRNA level of p16^INK4a or p19^ARF was also restored in knockdown BMI1 (left panel) or SUZ12 (right panel) stably infected BALB/c 3T3 cells. RT-PCR analysis was performed to detect the p16^INK4a, p19^ARF, or β-actin transcripts in BALB/c 3T3 cells as described under “Experimental Procedures.”