The silent information regulator(SIR2) family of genes are highly conserved from prokaryotes to eukaryotes and are involved in diverse processes,including transcriptional regulation,cell cycle progression,DNA-damage repair and aging. SIR2 contains a 323 amino acid catalytic core domain with a NAD-binding domain and a large groove which is the likely site of catalysis. SIR2 is widely expressed,highly expressed in heart,brain and skeletal muscle,while it is weakly expressed in placenta and lung. Down-regulated in many gliomas suggesting that it may act as a tumor suppressor gene in human gliomas possibly through the regulation of microtubule network. SIRT2 exists various isoforms and the molecular weight of isoforms are 35kDa,40 kDa,and 42 kDa.