TY - JOUR TI - Regulation of phospholipid synthesis in Saccharomyces cerevisiae by mRNA stability DO - https://doi.org/doi:10.7282/T3CJ8DFV PY - 2007 AB - In the yeast Saccharomyces cerevisiae, the most abundant phospholipid phosphatidylcholine is synthesized by the complementary CDP-diacylglycerol and Kennedy pathways. Using a cki1D eki1D mutant defective in choline kinase and ethanolamine kinase, we examined the consequences of a block in the Kennedy pathway on the regulation of phosphatidylcholine synthesis by the CDP-diacylglycerol pathway. The cki1D eki1D mutant exhibited increases in the synthesis of phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine via the CDP-diacylglycerol pathway. The increase in phospholipid synthesis correlated with increased activity levels of the CDP-diacylglycerol pathway enzymes phosphatidylserine synthase, phosphatidylserine decarboxylase, phosphatidylethanolamine methyltransferase, and phospholipid methyltransferase. However, other enzyme activities, including phosphatidylinositol synthase and phosphatidate phosphatase, were not affected in the cki1D eki1D mutant. For phosphatidylserine synthase, the enzyme catalyzing the committed step in the pathway, activity was regulated by increases in the levels of mRNA and protein. Decay analysis of CHO1 mRNA indicated that a dramatic increase in transcript stability was a major component responsible for the elevated level of phosphatidylserine synthase. We examined the decay pathway of CHO1 mRNA by analyzing the rates of transcript degradation in mutants defective in a specific mRNA decay pathway. When compared with the decay (t1/2 = 10-12 min) of the wild type control, the half-life of CHO1 mRNA was increased (t1/2 > 45 min) in the ccr4D, dcp1D, and xrn1D mutants defective in deadenylation, decapping, and 5’-to-3’ exonucleolytic degradation, respectively. The stability of CHO1 mRNA also increased in the ski4-1 mutant defective in the 3’-to-5’ exosome-mediated decay pathway. These results indicated that CHO1 mRNA in S. cerevisiae is degraded through the 5’-to-3’ and 3’-to-5’ decay pathways. We also found that CHO1 mRNA decay was defective in respiratory deficient mutants that were derived from wild type cells and from an eki1 D mutant. The respiratory inhibitor KCN caused a dose dependent increase in CHO1 mRNA stability. This increase in mRNA stability was recapitulated in a cox4D mutant defective in the cytochrome c oxidase enzyme. These results indicated that mitochondrial respiration was required for normal CHO1 mRNA decay. KW - Food Science KW - Saccharomyces cerevisiae KW - Messenger RNA KW - RNA editing LA - eng ER -