In this study, we investigated the roles of very long-chain fatty acid (VLCFA) synthesis by fatty acid elongase 3 (ELO3) in the regulation of telomere length and life span in the yeast Saccharomyces cerevisiae. Loss of VLCFA synthesis via deletion of ELO3 reduced telomere length, and reconstitution of the expression of wild type ELO3, and not by its mutant with decreased catalytic activity, rescued telomere attrition. Further experiments revealed that alterations of phytoceramide seem to be dispensable for telomere shortening in response to loss of ELO3. Interestingly, telomere shortening in elo3⌬ cells was almost completely prevented by deletion of IPK2 or KCS1, which are involved in the generation of inositol phosphates (IP4, IP5, and inositol pyrophosphates). Deletion of IPK1, which generates IP6, however, did not affect regulation of telomere length. Further data also suggested that elo3⌬ cells exhibit accelerated chronologic aging, and reduced replicative life span compared with wild type cells, and deletion of KCS1 helped recover these biological defects. Importantly, to determine downstream mechanisms, epistasis experiments were performed, and data indicated that ELO3 and YKU70/80 share a common pathway for the regulation of telomere length. More specifically, chromatin immunoprecipitation assays revealed that the telomere binding and protective function of YKu80p in vivo was reduced in elo3⌬ cells, whereas its non-homologues end-joining function was not altered. Deletion of KCS1 in elo3⌬ cells recovered the telomere binding and protective function of Ku, consistent with the role of KCS1 mutation in the rescue of telomere length attrition. Thus, these findings provide initial evidence of a possible link between Elo3-dependent VLCFA synthesis, and IP metabolism by KCS1 and IPK2 in the regulation of telomeres, which play important physiological roles in the control of senescence and aging, via a mechanism involving alterations of the telomere-binding/protection function of Ku.Very long-chain fatty acids (VLCFAs), 2 containing mainly 26 carbons in yeast, are synthesized from palmitoyl-CoA by microsomal fatty acid (FA) elongases (Elo1-3p) that catalyze the multistep chain elongation reactions (1-4). As summarized in Fig. 1A, the chain elongation, up to C24-FA, is catalyzed by both Elo2p and Elo3p, whereas elongation from C24-to C26-FA is exclusively catalyzed by Elo3p (2). Yeast sphingolipids contain predominantly C26-phytoceramide (5, 6) with hexacosanoic acid (C26-FA), which is a precursor for the synthesis of complex sphingolipids, such as inositol phosphorylceramide (IPC), mannosylinositol phosphorylceramide, and mannosyldiinositol phosphorylceramide. Null mutations of ELO3 (SUR4, YLR372W, SRE1, and VBM1), therefore, cause striking changes in the synthesis of sphingolipids and phosphatidylinositol/inositol phosphate metabolism (7-10), which are known to mediate diverse biological and signaling functions, including regulation of longevity, senescence, and telomere length (11-13).Telomeres are multifunction...