The 18S rRNA Methyltransferase DIMT-1 Regulates Lifespan in the Germline Later in Life

There is a marked dysregulation of the proteome as organisms age. Regulation of both protein production and degradation can become dysregulated as an organism ages. However, whether and how aging-responsive transcripts are selectively translated is unknown. Changes in the composition of the ribosome can lead to differential binding and translation of specific transcripts. Here we examined the role of ribosomal RNA (rRNA) methylation in maintaining appropriate translation of age-dependent transcripts. In a directed RNAi screen we identified the 18S rRNA N6’-dimethyl adenosine (m6,2A) methyltransferase, dimt-1, as a regulator of C. elegans lifespan and stress resistance. Lifespan extension induced by dimt-1 deficiency required a functional germline and the Rag GTPase, raga-1, which links amino acid sensing to mechanistic target of rapamycin (mTOR) complex (mTORC)1. Using an auxin-inducible degron tagged version of dimt-1 we demonstrate that DIMT-1 functions in the worms germline after mid-life to regulate lifespan. We further found that knock-down of dimt-1 leads to selective translation of transcripts important for stress resistance and lifespan regulation in the C. elegans germline in mid-life. Our findings highlight a new role for rRNA modifications such as m6,2A and ribosome heterogeneity more broadly, in maintaining appropriate translation later in life to promote healthy aging. To investigate the role of germline dimt-1 in regulating C. elegans lifespan, we IP'd FLAG-tagged germline ribosomes from dimt-1 knock down and control worms. The purified ribosome-bound transcripts were then subject to mRNA-seq. As a control, we also performed mRNA-seq on dimt-1 knock down and control worms using total RNA from whole-worm lysates. To further investigate the role of germline dimt-1 in regulating C. elegans lifespan, we IP'd FLAG-tagged muscle ribosomes from dimt-1 knock down and control worms as a separate control experiment. The purified ribosome-bound transcripts were then subject to mRNA-seq. As another control, we also performed mRNA-seq on dimt-1 knock down and control worms using total RNA from whole-worm lysates.