Resveratrol, a small molecule found in red wine, is reported to slow aging in simple eukaryotes and has been suggested as a potential calorie restriction mimetic. Resveratrol has also been reported to act as a sirtuin activator, and this property has been proposed to account for its anti-aging effects. We show here that resveratrol is a substrate-specific activator of yeast Sir2 and human SirT1. In particular, we observed that, in vitro, resveratrol enhances binding and deacetylation of peptide substrates that contain Fluor de Lys, a non-physiological fluorescent moiety, but has no effect on binding and deacetylation of acetylated peptides lacking the fluorophore. Consistent with these biochemical data we found that in three different yeast strain backgrounds, resveratrol has no detectable effect on Sir2 activity in vivo, as measured by rDNA recombination, transcriptional silencing near telomeres, and life span. In light of these findings, the mechanism accounting for putative longevity effects of resveratrol should be reexamined.

SIRT1 and other NAD-dependent deacetylases have been implicated in control of cellular responses to stress and in tumorigenesis through deacetylation of important regulatory proteins, including p53 and the BCL6 oncoprotein. Hereby, we describe the identification of a compound we named cambinol that inhibits NAD-dependent deacetylase activity of human SIRT1 and SIRT2. Consistent with the role of SIRT1 in promoting cell survival during stress, inhibition of SIRT1 activity with cambinol during genotoxic stress leads to hyperacetylation of key stress response proteins and promotes cell cycle arrest. Treatment of BCL6-expressing Burkitt lymphoma cells with cambinol as a single agent induced apoptosis, which was accompanied by hyperacetylation of BCL6 and p53. Because acetylation inactivates BCL6 and has the opposite effect on the function of p53 and other checkpoint pathways, the antitumor activity of cambinol in Burkitt lymphoma cells may be accomplished through a combined effect of BCL6 inactivation and checkpoint activation. Cambinol was well tolerated in mice and inhibited growth of Burkitt lymphoma xenografts. Inhibitors of NADdependent deacetylases may constitute novel anticancer agents. (Cancer Res 2006; 66(8): 4368-77)

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To probe the steric requirements for deacylation, we synthesized lysine-derived small molecule substrates and examined structure-reactivity relationships with various histone deacetylases. Rat liver, human HeLa, and human recombinant class I and II histone deacetylases (HDACs) as well as human recombinant NAD + -dependent SIRT1 (class III enzyme) were used in these studies. A benzyloxycarbonyl substituent on the R-amino group yielded the highest conversion rates. Replacing the -acetyl group with larger lipophilic acyl substituents led to a pronounced decrease in conversion by class I and II enzymes; the class III enzyme displayed a greater tolerance. Incubations with recombinant FLAG-tagged human HDACs 1, 3, and 6 showed a distinct subtype selectivity among small molecule substrates. The subtype selectivity of HDAC inhibitors could be predicted with these substrates and an easily obtainable mixture of HDAC subtypes.