Transient Structure Associated with the Spindle Pole Body Directs Meiotic Microtubule Reorganization in S. pombe

• Published in: Current biology Vol. 22; no. 7; pp. 562 - 574
• Main Authors: Funaya, Charlotta, Samarasinghe, Shivanthi, Pruggnaller, Sabine, Ohta, Midori, Connolly, Yvonne, Müller, Jan, Murakami, Hiroshi, Grallert, Agnes, Yamamoto, Masayuki, Smith, Duncan, Antony, Claude, Tanaka, Kayoko
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 10.04.2012; Cell Press
• Subjects: Cell Nucleus - physiology; Centrosomes; chromosome segregation; Chromosomes; Cytoskeleton; Differentiation; Dissolution; gene expression regulation; Meiosis; Microscopy, Fluorescence; Microtubule-Organizing Center - metabolism; Microtubules; Microtubules - metabolism; Molecular modelling; Phosphorylation; Prophase; Recombination; Schizosaccharomyces - metabolism; Schizosaccharomyces pombe; Schizosaccharomyces pombe Proteins - metabolism; Sex differentiation; Spindle Apparatus - metabolism; spindle pole bodies; spindle pole body; Spindles; Tomography; Tubulin; Tubulin - metabolism
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2012.02.042

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. 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. 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. [Display omitted] ► A novel specialized MTOC (rMTOC) organizes a meiotic radial microtubule (rMT) array ► rMTOC is transiently generated to reorganize MTs appropriate for differentiation ► Hrs1/Mcp6, a potential NudE ortholog, scaffolds the rMTOC ► Both phosphorylation and degradation of Hrs1/Mcp6 ensure rMTOC inactivation