SirT1 (UniProtKB/Swiss–Prot entry Q96EB6) is a NAD–dependent deacetylase, which regulates processes such as apoptosis and muscle differentiation by the deacetylation of key regulatory proteins. Deacetylation of lysine 382 of p53/TP53 by Sirt1 impairs its ability to induce the proapoptotic program and modulate cell senescence, whereas deacetylation of TAF1B represses rDNA transcription by the RNA polymerase I. SirT1 is also involved in HES1– and HEY2–mediated transcriptional repression and inhibits skeletal muscle differentiation by deacetylating PCAF and MYOD1. SirT1 is recruited to the nuclear bodies via its interaction with PML