Decreased RNA, and Increased RNA Oxidation, in Ribosomes from Early Alzheimer’s Disease

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.

Revenge of the NRD: Preferential Degradation of Nonfunctional Eukaryotic rRNA

Eukaryotic cells have several quality control systems that monitor the proper processing of RNAs during RNA biogenesis or the function of cytoplasmic mRNAs. A recent study in Molecular Cell by LaRiviere et al. (2006) shows that after production, mature rRNA is also subject to quality control and nonfunctional ribosomes are targeted for destruction by a novel ribosome surveillance mechanism.