S-adenosyl methionine synthetase SAMS-5 mediates dietary restriction-induced longevity in Caenorhabditis elegans.

S-adenosyl methionine synthetase (SAMS) catalyzes the biosynthesis of S-adenosyl methionine (SAM), which serves as a universal methyl group donor for numerous biochemical reactions. Previous studies have clearly demonstrated that SAMS-1, a C. elegans homolog of mammalian SAMS, is critical for dietary restriction (DR)-induced longevity in Caenorhabditis elegans. In addition to SAMS-1, three other SAMS paralogs have been identified in C. elegans. However, their roles in longevity regulation have never been explored. Here, we show that depletion of sams-5, but not sams-3 or sams-4, can extend lifespan in worms. However, the phenotypes and expression pattern of sams-5 are distinct from sams-1, suggesting that these two SAMSs might regulate DR-induced longevity via different mechanisms. Through the genetic epistasis analysis, we have identified that sams-5 is required for DR-induced longevity in a pha-4/FOXA dependent manner.