Understanding the biological mechanisms underlying aging and cancer predisposition remains a fundamentally important goal in biomedicine. The generation of a PASG hypomorphic mutant mouse model shows that PASG, an SNF2 family member, is essential for properly maintaining normal DNA methylation and gene expression patterns. Disruption of PASG leads to decreased incorporation of BrdU, accumulation of senescence-associated tumor suppressor genes, and increased senescence-associated beta-galactosidase as well as age-related phenotypes. These observations demonstrate that PASG plays a critical role in maintenance of tissue homeostasis, normal growth and longevity.