(a, b) NR2E1 knockdown by shRNA induces cellular senescence in IMR90. Knockdown efficiency of NR2E1 shRNA (a, left) is shown. The effect of NR2E1 knockdown on the percentage of SA-β-galactosidase positive cells (a, right) and cell growth (b) is shown. (c) NR2E1 knockdown by siRNA inhibits cell proliferation in IMR90, as shown by BrdU incorporation in IMR90 transfected with a scrambled siRNA or a siRNA targeting NR2E1 (right). The efficiency of NR2E1 knockdown was assessed by qRT-PCR (left). (d) NR2E1 knockdown results in a decrease in CBX7 level and an increase in p16INK4a and p21CIP1 levels in IMR90, as shown by CBX7 qRT-PCR (left), p16INK4a IF (middle) and p21CIP1 IF (right). (e) The effect of NR2E1 on senescence is dependent on p16INK4a and p21CIP1a. BrdU incorporation was assessed in IMR90 cells infected with an empty vector (vector) or vectors knocking down p16INK4a (shp16) or p21CIP1a (shp21) and then transfected with a scrambled siRNA or a siRNA targeting NR2E1.