using NuPAGE MES SDS running buffer (Thermo Fisher, Waltham, MA) and transferred
on PVDF membranes using Trans-Blot Turbo transfer system (Bio-Rad Laboratories,
Hercules, CA). Membranes were blocked with 5% nonfat milk, incubated with
primary antibodies overnight, washed three times with TBST, and probed with
respective secondary antibodies for 1 hour at room temperature.
For immunoprecipitation, cell lysates were rotated at 4 °C
overnight with 2 μg of SirT1 antibody that had been pre-coupled with 20
μl of protein A/G beads for 1 hour. Beads were rinsed and proteins
separated by SDS-polyacrylamide gel electrophoresis. Overexpressed FLAG-SirT1
was directly immunoprecipitated with anti-FLAG antibody coated magnetic beads.
Protein-protein interactions were identified by blotting for the respective
interacting protein using GAPDH, SirT1, and Ac-p53 antibodies. Membranes were
developed using the KwikQuant Western blot detection kit and images were
recorded using the KwikQuant imager (Kindle Biosciences, Greenwich, CT).