Scp160-Dependent mRNA Trafficking Mediates Pheromone Gradient Sensing and Chemotropism in Yeast

SummarymRNAs encoding polarity and secretion factors (POLs) target the incipient bud site in yeast for localized translation during division. In pheromone-treated cells we now find that these mRNAs are also localized to the yeast-mating projection (shmoo) tip. However, in contrast to the budding program, neither the She2 nor She3 proteins are involved. Instead, the Scp160 RNA-binding protein binds POL and mating pathway mRNAs and regulates their spatial distribution in a Myo4- and cortical ER-dependent fashion. RNA binding by Scp160 is stimulated by activation of Gpa1, the G protein α subunit regulated by the pheromone receptor, and is required for pheromone gradient sensing, as well as subsequent chemotropic growth and cell-cell mating. These effects are incurred independently of obvious changes in translation; thus, mRNA trafficking is required for chemotropism and completion of the mating program. This is, to our knowledge, the first demonstration of ligand-activated RNA targeting in the development of a simple eukaryote.

Graphical AbstractFigure optionsDownload as PowerPoint slideHighlights
► mRNAs encoding polarity and mating pathway components localize to the shmoo tip
► RNA delivery depends upon Myosin 4 and the transport of cortical endoplasmic reticulum
► Scp160 is a pheromone-activated RNA-binding protein that binds and delivers mRNAs
► Loss of RNA binding to Scp160 blocks chemotropism and inhibits mating