A sirtuin's role in preventing senescence by protecting ribosomal DNA.

Ribosomes are encoded by many copies of ribosomal DNA (rDNA) packed into the nucleolus. High rates of transcription combined with highly repetitive sequences render rDNA loci particularly vulnerable to genomic instability, a proposed underlying cause of cellular senescence. The molecular mechanisms that maintain rDNA stability have remained unclear. A new paper elucidates a sirtuin-dependent mechanism that protects rDNA loci from genomic instability and prevents cellular senescence via heterochromatin silencing mediated by the chromatin remodeler SNF2H. This finding extends our understanding of chromatin dynamics within rDNA regions and offers new mechanistic insights into aging-related pathologies associated with genomic instability.