Fig 1.

Induction of SIRT1 expression by serum starvation in human cell lines is dependent on p53. The cells were grown under normal nutrients (C) or under serum starvation (S) for 16 hrs. Real-time PCR analysis and Western blot were performed as described in the Material and Methods. Significant induction of SIRT1 expression was observed in p53-expressing cells (HEK293, HeLa, U2OS and HepG2), but not p53-null cells (Saos-2 and Hep3B). GAPDH RNA and β-actin protein were used as normalizing control for RNA and protein quantification assay, respectively. (A) and (B), mRNA levels quantified with real-time PCR. (C) Protein levels determined by Western blot.