Histone methylation plays crucial roles in the development, gene regulation and maintenance of stem cell pluripotency in mammals. Recent work shows that histone methylation is associated with aging, yet the underlying mechanism remains unclear. In this work, we identified a class of histone 3 lysine 9 mono-/dimethyltransferase genes (met-2, set-6, set-19, set-20, set-21, set-32andset-33), mutations in which induce synergistic lifespan extension in the long-lived DAF-2 (IGF-1 receptor) mutant inC. elegans. These histone methyltransferase plusdaf-2double mutants not only exhibited an average lifespan nearly three times that of wild-type animals and a maximal lifespan of approximately 100 days, but also significantly increased resistance to oxidative and heat stress. Synergistic lifespan extension depends on the transcription factor DAF-16 (FOXO). mRNA-seq experiments revealed that the mRNA levels of class I DAF-16 target genes, which are activated by DAF-16, were further elevated in the double mutants. Among these genes,F35E8.7, nhr-62, sod-3, asm-2andY39G8B.7are required for the lifespan extension of thedaf-2;set-21double mutant. In addition, treatingdaf-2animals with the H3K9me1/2 methyltransferase G9a inhibitor also extends lifespan and increases stress resistance. Therefore, investigation of DAF-2 and H3K9me1/2 methyltransferase deficiency-mediated synergistic longevity will contribute to a better understanding of the molecular mechanisms of aging and therapeutic applications.
