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

ABSTRACT: 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.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE237802 | GEO | 2024/06/06

REPOSITORIES: GEO

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Project description:The plasticity of ageing suggests that longevity may be controlled epigenetically by specific alterations in chromatin state. The link between chromatin and ageing has mostly focused on histone deacetylation by the Sir2 family1, 2, but less is known about the role of other histone modifications in longevity. Histone methylation has a crucial role in development and in maintaining stem cell pluripotency in mammals3. Regulators of histone methylation have been associated with ageing in worms4, 5, 6, 7 and flies8, but characterization of their role and mechanism of action has been limited. Here we identify the ASH-2 trithorax complex9, which trimethylates histone H3 at lysine 4 (H3K4), as a regulator of lifespan in Caenorhabditis elegans in a directed RNA interference (RNAi) screen in fertile worms. Deficiencies in members of the ASH-2 complex—ASH-2 itself, WDR-5 and the H3K4 methyltransferase SET-2—extend worm lifespan. Conversely, the H3K4 demethylase RBR-2 is required for normal lifespan, consistent with the idea that an excess of H3K4 trimethylation—a mark associated with active chromatin—is detrimental for longevity. Lifespan extension induced by ASH-2 complex deficiency requires the presence of an intact adult germline and the continuous production of mature eggs. ASH-2 and RBR-2 act in the germline, at least in part, to regulate lifespan and to control a set of genes involved in lifespan determination. These results indicate that the longevity of the soma is regulated by an H3K4 methyltransferase/demethylase complex acting in the C. elegans germline. There are 23 samples in total. ASH-2 knock-down increases lifespan in a germline dependent manner. We examined ASH-2 regulated genes that are dependent on the presence of an intact germline using WT or glp-1(e2141ts) mutant worms which develop only 5-15 meiotic germ cells treated with either empty vector (EV) or ash-2 RNAi. We examined gene expression at the L3 stage (when we observe changes in H3K4me3) and at a mid life stage (day 8). The majority of ASH-2 controlled genes were regulated in a germline dependent manner. Samples were collected in triplicate for each condition (but Day 8 N2 (WT) E.V. #3 was excluded from all analysis due to quality issues).

Project description:One of the most important issues in the study of aging is to discover compounds with longevity-promoting activity and to unravel their underlying mechanisms. Queen honey bees are continuously fed royal jelly (RJ), and they live more than 10 times longer than hive workers, derived from the same diploid genome, which are fed it only for a short period of time during their larval stages. Therefore, RJ is likely to contain longevity-promoting agents for queens. RJ has been reported to possess diverse pharmacological properties. Furthermore, protease-treated RJ (pRJ) has additional beneficial activities. How RJ and pRJ exert these effects and which components in them play a critical role is largely unknown. The evolutionally conserved mechanisms that control lifespan have been indicated. The nematode Caenorhabditis elegans has been widely used for study of aging and longevity, due to its relatively short lifespan and well-established genetic pathways. The purpose of the present study was to elucidate whether RJ and its related substances contain the life span-extending activity in C. elegans and to obtain some insight into the active agents and their mechanisms. We found that both RJ and pRJ extended the lifespan of C. elegans. The life span-extending activity of pRJ was enriched by ODS column chromatography (pRJ-Fraction 5). pRJ-Fr. 5 extended the life span partly by acting through the FOXO transcription factor DAF-16, the activation of which is known to promote longevity in C. elegans by reducing insulin/IGF-1 signaling (IIS). pRJ-Fr. 5 induced changes in the expression of 3 genes encoding insulin-like peptides. Moreover, pRJ-Fr. 5 and reduced IIS shared some common features in terms of their effect on gene expression, such as up-regulation of dod-3 and down-regulation of dod-19, dao-4 and fkb-4. The dod-19 is a previously identified life span determinant in C. elegans, and the fkb-4 encodes a homologue of the mammalian FK506-binding protein. 10-Hydroxy-2-decenoic acid (10-HDA), which was present in high concentration in pRJ-Fr. 5, increased the lifespan independently of DAF-16 activity.These results demonstrate that RJ and its related substances extended the life span in C. elegans, suggesting that RJ may contain longevity-promoting factors common to diverse species across phyla. pRJ-Fr. 5 had higher life span-extending activity than either RJ or pRJ and extended the life span in part through the IIS-DAF-16 pathway. We provide the first evidence that 10-HDA, a defined natural product in RJ, extended organismal lifespan. It is noteworthy that 10-HDA performed its lifespan-extending function through a mechanism totally different from the IIS-DAF-16 pathway. Further search and characterization of the lifespan-extending agents in RJ and pRJ may broaden our understanding of the gene network of longevity regulation in diverse species and provide the possibility for nutraceutical interventions in the aging process. C. elegans N2 hermaphrodites were untreated or treated with pRJ-Fr. 5 (25mg/ml) for 24 h starting at the larval 4 (L4) stage.

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

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