Involved in silencing within the mating-type region, at the telomeres, and according to PubMed:12867036 also within centromeric DNA regions. Required for the localization of swi6 to the telomeres, silent mating type region, and according to PubMed:12867036 to the centromeric DNA regions. According to PubMed:15545655 not required for the localization of swi6 to centromeric foci. Deacetylates histone H3 on 'Lys-9' and 'Lys-16' of histone H4. This has a direct role in heterochromatin assembly. H2O + N(6)-acetyl-L-lysyl-[protein] + NAD(+) = 2''-O-acetyl-ADP-D-ribose + L-lysyl-[protein] + nicotinamide Binds 1 zinc ion per subunit. Nuclear throughout the cell cycle. Binds to centromeres, telomeric sites and sites between the silent mating-type loci. Belongs to the sirtuin family. Class I subfamily.