Ribosomal RNA methylation regulation of longevity and stress resistance

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Project Summary The goal of this project is to understand how ribosomal RNA methylation can regulate translation of specific proteins to regulate aging. Disruption of the proteome is a hallmark of aging. Having the capacity to express the appropriate protein in response to environmental cues is an essential and evolutionarily conserved process. Therefore, preserving the proteome is critical for maintaining organismal health and healthy aging. However, how aging-responsive mRNAs are selectively translated is unknown. We recently identified that ribosomal RNA methylation could facilitate the translation of a specific subset of proteins. Additionally, we characterized how ribosome occupancy changes as an organism ages and determined that changes in ribosomal DNA methylation are sufficient to project the organismal age. Whether ribosomal RNA methylation plays a role in preserving proteome integrity as organisms age is still unclear. We have recently found that enzymes which regulate RNA methylation and RNA methylation itself are dysregulated during aging and in response to stress. We found that an N6-adenosine methyltransferase, METL-5, directly methylates adenosine 1717 on 18S ribosomal RNA in C. elegans. Methylation of adenosine 1717 enhances ribosomal binding and selective translation of specific mRNAs. Our preliminary data shows that metl-5 deficient animals grow normally under homeostatic conditions; however, metl-5 mutants are resistant to a variety of stresses, including heat shock and UV irradiation. Thus, methylation of a specific residue of 18S rRNA by METL-5 selectively enhances translation of specific transcripts to regulate stress resistance. However, whether rRNA methylation more broadly can regulate age and stress-responsive translation and whether this dysregulation drives the aging process is still unknown. By performing a directed RNAi screen, we identified additional rRNA methyltransferases that when deleted increase C. elegans lifespan. These preliminary findings suggest that ribosomal RNA methylation can facilitate selective translation of specific transcripts providing another layer of regulation of the stress response and aging. Capitalizing on this preliminary data we will use genetic, biochemical, and molecular approaches both in vitro and in vivo to dissect the role of rRNA methylation in regulating aging and stress resistance. Our underlying hypothesis is that rRNA methylation promotes ribosome heterogeneity in response to stress conditions and aging to facilitate the appropriate translation of stress resistance transcripts.