title: Transient structure associated with the spindle pole body directs meiotic microtubule reorganization in S. pombe.
abstract: BACKGROUND
  Vigorous chromosome movements driven by cytoskeletal assemblies are a widely conserved feature of sexual differentiation to facilitate meiotic recombination. In fission yeast, this process involves the dramatic conversion of arrays of cytoplasmic microtubules (MTs), generated from multiple MT organizing centers (MTOCs), into a single radial MT (rMT) array associated with the spindle pole body (SPB), the major MTOC during meiotic prophase. The rMT is then dissolved upon the onset of meiosis I when a bipolar spindle emerges to conduct chromosome segregation. Structural features and molecular mechanisms that govern these dynamic MT rearrangements are poorly understood.
  
  
  RESULTS
  Electron tomography of the SPBs showed that the rMT emanates from a newly recognized amorphous structure, which we term the rMTOC. The rMTOC, which resides at the cytoplasmic side of the SPB, is highly enriched in γ-tubulin reminiscent of the pericentriolar material of higher eukaryotic centrosomes. Formation of the rMTOC depends on Hrs1/Mcp6, a meiosis-specific SPB component that is located at the rMTOC. At the onset of meiosis I, Hrs1/Mcp6 is subject to strict downregulation by both proteasome-dependent degradation and phosphorylation leading to complete inactivation of the rMTOC. This ensures rMT dissolution and bipolar spindle formation.
  
  
  CONCLUSIONS
  Our study reveals the molecular basis for the transient generation of a novel MTOC, which triggers a program of MT rearrangement that is required for meiotic differentiation.
authors.affiliation: Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Funaya
authors.forename: Shivanthi
authors.initials: S
authors.lastname: Samarasinghe
authors.forename: Sabine
authors.initials: S
authors.lastname: Pruggnaller
authors.forename: Midori
authors.initials: M
authors.lastname: Ohta
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Connolly
authors.forename: Jan
authors.initials: J
authors.lastname: Müller
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Murakami
authors.forename: Agnes
authors.initials: A
authors.lastname: Grallert
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Duncan
authors.initials: D
authors.lastname: Smith
authors.forename: Claude
authors.initials: C
authors.lastname: Antony
authors.forename: Kayoko
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D002467:Cell Nucleus / Q000502:physiology*; D008540:Meiosis; D008856:Microscopy, Fluorescence; D022101:Microtubule-Organizing Center / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
chemical_list: C507869:Hrs1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D014404:Tubulin