(A) The interaction between SIRT1 and p53 in WT and
Pkd1-null MEK cells was examined by co-IP using either anti-SIRT1 or
anti-p53 antibody. IgG was used as a negative control. (B) Western blot
analysis of p53 and acetyl-p53 expression from whole cell lysates of WT MEK,
Pkd1-null MEK, PH2, and PN24 cells. Acetyl-p53 expression was
decreased in Pkd1-null MEK versus WT MEK cells, whereas p53 expression
was almost at same levels in these cells. (C and D) Knockdown
of SIRT1 with siRNA or inhibition of SIRT1 with nicotinamide increased p53 acetylation,
but did not affect p53 expression, in Pkd1-null MEK cells and PN24
cells that were (C) transfected with SIRT1 siRNA for 48 hours or
(D) treated with 10 mM nicotinamide for 24 hours. *P
0.05, **P 0.01.