title: Synergistic role of fission yeast Alp16GCP6 and Mzt1MOZART1 in γ-tubulin complex recruitment to mitotic spindle pole bodies and spindle assembly.
abstract: In fission yeast, γ-tubulin ring complex (γTuRC)-specific components Gfh1(GCP4), Mod21(GCP5), and Alp16(GCP6) are nonessential for cell growth. Of these deletion mutants, only alp16Δ shows synthetic lethality with temperature-sensitive mutants of Mzt1(MOZART1), a component of the γTuRC required for recruitment of the complex to microtubule-organizing centers. γ-Tubulin small complex levels at mitotic spindle pole bodies (SPBs, the centrosome equivalent in fungi) and microtubule levels for preanaphase spindles are significantly reduced in alp16Δ cells but not in gfh1Δ or mod21Δ cells. Furthermore, alp16Δ cells often form monopolar spindles and frequently lose a minichromosome when the spindle assembly checkpoint is inactivated. Alp16(GCP6) promotes Mzt1-dependent γTuRC recruitment to mitotic SPBs and enhances spindle microtubule assembly in a manner dependent on its expression levels. Gfh1(GCP4) and Mod21(GCP5) are not required for Alp16(GCP6)-dependent γTuRC recruitment. Mzt1 has an additional role in the activation of the γTuRC for spindle microtubule assembly. The ratio of Mzt1 to γTuRC levels for preanaphase spindles is higher than at other stages of the cell cycle. Mzt1 overproduction enhances spindle microtubule assembly without affecting γTuRC levels at mitotic SPBs. We propose that Alp16(GCP6) and Mzt1 act synergistically for efficient bipolar spindle assembly to ensure faithful chromosome segregation.
authors.affiliation: Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London WC2A 3LY, United Kingdom hirohisa.masuda@nih.gov.
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Masuda
authors.affiliation: Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London WC2A 3LY, United Kingdom Hiroshima Research Center for Healthy Aging, Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Toda
mesh_terms: D000595:Amino Acid Sequence; D018385:Centrosome / Q000378:metabolism; D020090:Chromosome Segregation; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D022101:Microtubule-Organizing Center / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D064048:Spindle Pole Bodies / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism*
chemical_list: C473565:Alp16 protein, S pombe; C494594:Gfh1 protein, S pombe; D008869:Microtubule-Associated Proteins; C000589192:Mzt1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D014404:Tubulin