Current Biology
Volume 22, Issue 7, 10 April 2012, Pages 562-574
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Article
Transient Structure Associated with the Spindle Pole Body Directs Meiotic Microtubule Reorganization in S. pombe

https://doi.org/10.1016/j.cub.2012.02.042Get rights and content
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Summary

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.

Highlights

► 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

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Present address: Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr-Gasse 3, 1030 Wien, Austria

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These authors contributed equally to this work