Figure 4. SIRT1 destabilizes WRN protein.

A, Flag-WRN alone or with SIRT1 was transfected into HEK293 cells. Cell lysates were subjected to SDS-PAGE and Western blotting with anti-WRN, anti-SIRT1 and anti-β-Actin antibodies. B, endogenous WRN protein level was decreased by SIRT1. Vector or SIRT1 was transfected into HEK293 cells. Cell lysates were analyzed by Western blot with anti-WRN, anti-SIRT1, and anti-β-actin antibodies. C, endogenous WRN protein level was increased by SIRT1 knockdown. HEK293 cells were transfected with siRNA for SIRT1 or GFP. Cell lysates were analyzed by Western blot with anti-WRN, anti-SIRT1, and anti-β-actin antibodies. All the experiments were repeated at least three times. The bands of WRN proteins were quantified by ImageJ software.