A metabolic function for phospholipid and histone methylation

S-adenosylmethionine (SAM) is the methyl donor for biological methylation modifications that regulate protein and nucleic acid functions. Here we show that methylation of a phospholipid, phosphatidylethanolamine (PE), is the major consumer of SAM in budding yeast. The induction of phospholipid biosynthetic genes is accompanied by induction of the enzyme that hydrolyzes S-adenosylhomocysteine (SAH), a product and inhibitor of methyltransferases. Beyond its function for the synthesis of phosphatidylcholine (PC), the methylation of PE facilitates the turnover of SAM for the synthesis of cysteine and glutathione. Strikingly, cells that lack PE methylation accumulate SAM, which leads to hypermethylation of histones and the major phosphatase PP2A, dependency on cysteine, and sensitivity to oxidative stress. Without PE methylation, particular sites on histones then become methyl sinks to enable the turnover of SAM. These findings reveal an unforeseen metabolic function for phospholipid and histone methylation intrinsic to the life of a cell. Overall design: Two biological replicates of wild type and cho2? cells in YPL media, in SL media after 1 hour and in SL media after 3 hour were collected for sequencing.