MPA-induced p53 activation requires the ribosomal proteins L5 and
L11. A, ablation of endogenous L5 by siRNA inhibits MPA-induced
p53. U2OS cells were transfected with scrambled or L5 siRNA for 48 h as
indicated. Twelve hours before harvesting, the cells were treated with
methanol (lanes 1 and 3) or 10 μmol/liter MPA (lanes
2 and 4). Cell lysates were assayed for expression of p53, p21,
and MDM2 by immunoblotting with specific antibodies. B, ablation of
endogenous L11 by siRNA inhibits MPA-induced p53. U2OS cells were transfected
with scrambled or L11 siRNA for 48 h as indicated. Twelve hours before
harvesting, the cells were treated with methanol (lanes 1 and
2) or 10 μmol/liter MPA (lanes 3 and 4). Cell
lysates were assayed for expression of p53, p21, and MDM2 by immunoblot with
specific antibodies. C and D, ablation of endogenous L5 or
L11 by siRNA inhibits the levels of p21 and mdm2 mRNA induced by MPA. Total
RNAs were prepared from cells transfected with scrambled, L5, or L11 siRNA
followed by treatment with methanol or MPA as above (A or B)
and retrotranscribed. Real-time PCR analysis was then conducted to determine
the expression of the mdm2 (C) and p21 (D) mRNA levels. The
expression of GAPDH mRNA was used as control.