A Late-acting Quality Control Process for Mature Eukaryotic RRNAs

Ribosome biogenesis is a multifaceted process involving a host of trans-acting factors mediating numerous chemical reactions, RNA conformational changes, and RNA-protein associations. Given this high degree of complexity, tight quality control is likely crucial to ensure structural and functional integrity of the end products. We demonstrate that ribosomal RNAs (rRNAs) containing individual point mutations, in either the 25S peptidyl transferase center or 18S decoding site, that adversely affect ribosome function are strongly downregulated in Saccharomyces cerevisiae. This downregulation occurs via decreased stability of the mature rRNA contained in fully assembled ribosomes and ribosomal subunits. Thus, eukaryotes possess a quality-control mechanism, nonfunctional rRNA decay (NRD), capable of detecting and eliminating the rRNA component of mature ribosomes.