Yeast phospholipid biosynthesis is linked to mRNA localization

Abstract

Localization of mRNAs and local translation are universal features in eukaryotes and contribute to cellular asymmetry and differentiation. In Saccharomyces cerevisiae, localization of mRNAs that encode membrane proteins requires the She protein machinery including the RNA-binding protein She2p as well as movement of the cortical endoplasmic reticulum (cER) to the yeast bud. In a screen for ER-specific proteins necessary for directional transport of WSC2 and EAR1 mRNAs, we have identified enzymes of the phospholipid metabolism. Loss of the phospholipid methyltransferase Cho2p, which showed the strongest impact on mRNA localization, disturbs mRNA localization as well as ER morphology and segregation due to an increase in cellular phosphatidylethanolamine (PE). Mislocalized mRNPs containing She2p co-localize with aggregated cER structures suggesting entrapment of mRNA and She2p by the elevated PE level, which is confirmed by elevated binding of She2p to PE-containing liposomes. These findings underscore the importance of ER membrane integrity in mRNA transport.