Mutations that Allow SIR2 Orthologs to Function in a NAD+-Depleted Environment

• Published in: Cell reports (Cambridge) Vol. 18; no. 10; pp. 2310 - 2319
• Main Authors: Ondracek, Caitlin R., Frappier, Vincent, Ringel, Alison E., Wolberger, Cynthia, Guarente, Leonard
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 07.03.2017; Elsevier
• Subjects: Acetylation; adaptive mutations; aging; Humans; kinetic analyses; Kinetics; Models, Molecular; Mutation - genetics; NAD; NAD - metabolism; predictive protein modeling; Protein Stability; Saccharomyces cerevisiae - metabolism; Sequence Homology, Amino Acid; Sir2; SIRT1; Sirtuin 2 - chemistry; Sirtuin 2 - genetics; Substrate Specificity; yeast replicative lifespan; NAD; Sir2; kinetic analyses; predictive protein modeling; adaptive mutations; aging; SIRT1; yeast replicative lifespan; NAD(+)
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2017.02.031

Sirtuin enzymes depend on NAD+ to catalyze protein deacetylation. Therefore, the lowering of NAD+ during aging leads to decreased sirtuin activity and may speed up aging processes in laboratory animals and humans. In this study, we used a genetic screen to identify two mutations in the catalytic domain of yeast Sir2 that allow the enzyme to function in an NAD+-depleted environment. These mutant enzymes give rise to a significant increase of yeast replicative lifespan and increase deacetylation by the Sir2 ortholog, SIRT1, in mammalian cells. Our data suggest that these mutations increase the stability of the conserved catalytic sirtuin domain, thereby increasing the catalytic efficiency of the mutant enzymes. Our approach to identifying sirtuin mutants that permit function in NAD+-limited environments may inform the design of small molecules that can maintain sirtuin activity in aging organisms. [Display omitted] •Adaptive mutations in yeast Sir2 permit function with low NAD+•Structural rigidity of catalytic domain and overall protein stability is enhanced•Catalytic efficiency is increased in mutant enzymes•Mutants increase yeast replicative lifespan and deacetylation of mammalian substrates Ondracek et al. report the identification of two adaptive mutations in yeast Sir2 that allow the enzyme to function in an NAD+-depleted environment by enhancing protein stability and increasing enzyme catalysis, which increases yeast replicative lifespan and deacetylation of in vivo substrates by the Sir2 ortholog, SIRT1, in mammalian cells.