SIRT1 and Huntington disease: In contrast, whilst we found that the acetylation levels of endogenous P53 were equivalent in HD as compared to WT littermate brains in presymptomatic mice (i.e. 4 week R6/2 and 2 month HdhQ150 homozygotes) (Fig 2A and 2B), the level of AcP53 was significantly higher (≥ 1.5 fold) in samples from early symptomatic R6/2 mice (9 weeks) and late stage symptomatic R6/2 (14 weeks) and HdhQ150 homozygous (22 months) mice (Fig 2A and 2B and S2A and S2B Fig), suggesting that SIRT1 activity becomes impaired in the HD mouse brain.