NAD-dependent histone deacetylase involved in heterochromatic silencing. Mildly suppresses the heterochromatin-mediated silencing phenomenon known as position-effect variegation (PEV). Required for epigenetic silencing of the polycomb group proteins. Has histone H4 deacetylase activity in vitro. Required maternally for establishing proper segmentation of the embryo. Involved in sex determination. May be involved in the regulation of life span. H2O + N(6)-acetyl-L-lysyl-[protein] + NAD(+) = 2''-O-acetyl-ADP-D-ribose + L-lysyl-[protein] + nicotinamide Binds 1 zinc ion per subunit. Optimum pH is 9. Interacts with the transcriptional repressors hairy (h) and deadpan (dpn); via basic domains. Associates with the Esc/E(z) histone methyltransferase complex. Interacts directly with E(z) and HDAC1/Rpd3. Causes lethality during development. Induced silencing shortens life span. Belongs to the sirtuin family. Class I subfamily.