Reference: Ponnusamy S, et al. (2008) Regulation of Telomere Length by Fatty Acid Elongase 3 in Yeast: INVOLVEMENT OF INOSITOL PHOSPHATE METABOLISM AND Ku70/80 FUNCTION. J Biol Chem 283(41):27514-24

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Abstract


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 yeast Saccharomyces cerevisiae. Loss of VLCFA synthesis via deletion of ELO3 reduced telomere length, and reconstitution of the expression of wt 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 elo3D 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 elo3D cells exhibit accelerated chronologic aging, and reduced replicative life span compared to wild type cells, and deletion of KCS1 helped recover these biological defects. Importantly, to determine down-stream 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 elo3D cells, whereas its non-homologues end-joining (NHEJ) function was not altered. Deletion of KCS1 in elo3D 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.

Reference Type
Journal Article
Authors
Ponnusamy S, Alderson NL, Hama H, Bielawski J, Jiang JC, Bhandari R, Snyder SH, Jazwinski SM, Ogretmen B
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