Modulation of the RNAse P/MRP complex and mitochondrial ribosome enhances cytosolic ribosome coordination and sustains longevity

Aging is accompanied by a progressive decline in protein synthesis and ribosome abundance, yet paradoxically, genetic or pharmacological attenuation of translation extends lifespan across species. Whether the age-associated decline in translation is adaptive or reflects a pathological failure of ribosome homeostasis remains unclear. Here, we show that shortened lifespan is driven by dysregulated ribosome biogenesis (RiBi) and impaired ribosome assembly. Using Caenorhabditis elegans ncl-1 loss-of-function mutants as a model of accelerated aging, we find that nucleolar enlargement coincides with decoupling of precursor and mature rRNA, ribosomal protein (RP) transcripts, and protein abundance, loss of RP stoichiometry, defective ribosomal subunit joining, and compromised proteostasis. Strikingly, lifespan can be restored downstream of the nucleolus by targeting either the RNAse P/MRP complex or the mitochondrial ribosome. These interventions rebalance mature rRNA and RP abundance, improve ribosomal assembly, and reduce protein aggregation despite persistent nucleolar enlargement and elevated pre-rRNA levels. Our findings identify accelerated age-associated ribosome dysfunction as a qualitative failure of ribosomal biogenesis, and demonstrate that restoring ribosomal homeostasis is sufficient to improve proteostasis and extend lifespan.