Figure 1.
Oxidative stress reduces Sir2/SIRT1-mediated repetitive DNA silencing in yeast and mammalian cells. (A–C). Effects of H2O2 on yeast aging. (A) H2O2 causes loss of silencing at the mating type loci. Shown is the fraction of GFP+ cells in 2xSIR2 and WT cells. Unless otherwise noted, P values are based on Student’s two-tailed t test with #P≤ 0.1, *P≤ 0.05, **P≤ 0.01, ***P≤ 0.001. (B) Frequency of H2O2-induced rDNA recombination in the absence presence of extra Sir2 (WT and Sir2 o/e). (C) Replicative lifespan of WT and 2xSIR2 cells grown in the absence or presence of 1 mM H2O2. (D) Mouse SIRT1 binds to repetitive genomic DNA. ChIP for SIRT1 or control immunoglobulin (Ig) at major satellite repeats in the absence or presence of NAM (25 mM) (E) q-PCR analysis of ChIP experiments using antibodies specific for SIRT1 or H1AcK26. ES cells were left untreated or treated with H2O2 (2 mM) or NAM for 1 h. (F) Oxidative stress increases transcription of satellite repeat DNA. ES cells were treated with NAM for 24 h or with H2O2 for 1 h, followed by 23 h recovery. (G) Cells with a targeted extra copy of SIRT1 and control cells were treated with H2O2 and analyzed as in (F). The inset shows a Western blot of SIRT1 in WT (black) and SIRT1 overexpressing ES cells (white). Data are represented as mean +/− SEM.