title: PolyQ-dependent RNA-protein assemblies control symmetry breaking.
abstract: Dendritic growth in fungi and neurons requires that multiple axes of polarity are established and maintained within the same cytoplasm. We have discovered that transcripts encoding key polarity factors including a formin, Bni1, and a polarisome scaffold, Spa2, are nonrandomly clustered in the cytosol to initiate and maintain sites of polarized growth in the fungus Ashbya gossypii. This asymmetric distribution requires the mRNAs to interact with a polyQ-containing protein, Whi3, and a Pumilio protein with a low-complexity sequence, Puf2. Cells lacking Whi3 or Puf2 had severe defects in establishing new sites of polarity and failed to localize Bni1 protein. Interaction of mRNAs with Whi3 and Puf2 promotes enrichment of transcripts at established sites of polarized growth and clustering of polarity transcripts throughout the cell body. Thus, aggregation-prone proteins make functional assemblies to position polarity transcripts, and nonrandom positioning of transcripts is required for symmetry-breaking events. This reveals a physiological function for polyQ-driven assemblies in regulating cell polarity.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755.
authors.forename: ChangHwan
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755.
authors.forename: Patricia
authors.initials: P
authors.lastname: Occhipinti
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 amy.gladfelter@dartmouth.edu.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Gladfelter
mesh_terms: D003600:Cytosol / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004718:Saccharomycetales / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D008840:Microfilament Proteins; D046912:Multiprotein Complexes; D010455:Peptides; D012331:RNA, Fungal; D016601:RNA-Binding Proteins; C097188:polyglutamine