The target of rapamycin (TOR) pathway regulates cell growth and aging in various organisms. In Saccharomyces cerevisiae, silent information regulator 2 (Sir2) modulates cellular senescence. Moreover, Sir2 plays a crucial role in promoting ribosomal DNA (rDNA) stability and longevity under TOR inhibition. Here we review the implication of rDNA stabilizers in longevity, discuss how Sir2 stabilizes rDNA under TOR inhibition and speculate on the link between sumoylation and Sir2-related pro-aging pathways.