Figure 1.

Identification of a novel protein complex containing SIRT1 and the PP4 phosphatase complex. (A) Schematic representation of the SIRT1 purification from HeLaS3 nuclear extracts (NE) including the buffers used (BC or BD) and a range of KCl gradient concentrations (from 40 mM to 1 M) depending on each chromatographic step (see Methods and Supplementary information). (B, C) Silver stained SDS-gel (B) and western-blot (C) of the anion-exchange MonoQ column, the final chromatography step of the purification. Fractions 23–25 were pooled and analyzed by mass spectrometry. The analysis showed that PP4 complex components PP4c, PP4R2, PP4R3α and PP4R3β co-fractionate with SIRT1 (Supplementary Table S1).