Centrosomes are important microtubule-organizing centers (MTOCs) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) are found in many cell types. Their composition and structure are only poorly understood. Here, we analyzed nuclear MTOCs (spindle-pole bodies, SPBs) and septal MTOCs in Aspergillus nidulans They both contain γ-tubulin along with members of the family of γ-tubulin complex proteins (GCPs). Our data suggest that SPBs consist of γ-tubulin small complexes (γ-TuSCs) at the outer plaque, and larger γ-tubulin ring complexes (γ-TuRC) at the inner plaque. We show that the MztA protein, an ortholog of the human MOZART protein (also known as MZT1), interacted with the inner plaque receptor PcpA (the homolog of fission yeast Pcp1) at SPBs, while no interaction nor colocalization was detected between MztA and the outer plaque receptor ApsB (fission yeast Mto1). Septal MTOCs consist of γ-TuRCs including MztA but are anchored through AspB and Spa18 (fission yeast Mto2). MztA is not essential for viability, although abnormal spindles were observed frequently in cells lacking MztA. Quantitative PALM imaging revealed unexpected dynamics of the protein composition of SPBs, with changing numbers of γ-tubulin complexes over time during interphase and constant numbers during mitosis.This article has an associated First Person interview with the first author of the paper.

中文翻译：

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构巢曲霉的纺锤极体是不对称的，并且包含数量不断变化的γ-微管蛋白复合物。

中心体是动物细胞中重要的微管组织中心（MTOC）。此外，在许多细胞类型中都发现了非中心体MTOC（ncMTOC）。对其组成和结构了解甚少。在这里，我们分析了构巢曲霉中的核MTOC（纺锤体，SPB）和间隔MTOC。它们都包含γ-微管蛋白以及γ-微管蛋白复合蛋白（GCP）家族的成员。我们的数据表明，SPB由位于外部斑块的γ-微管蛋白小复合物（γ-TuSCs）和位于内部斑块的较大的γ-微管蛋白环复合物（γ-TuRC）组成。我们显示，MztA蛋白是人类MOZART蛋白的直系同源物（也称为MZT1），在SPBs与内部噬菌斑受体PcpA（裂变酵母Pcp1的同源物）相互作用，而在MztA和外部噬菌斑受体ApsB（裂变酵母Mto1）之间未发现相互作用或共定位。间隔MTOC由包括MztA在内的γ-TuRC组成，但通过AspB和Spa18（裂殖酵母Mto2）锚定。尽管缺乏MztA的细胞中经常观察到异常纺锤体，但MztA对存活力不是必需的。定量PALM成像揭示了SPBs蛋白质组成的出乎意料的动态，相间的γ-微管蛋白复合物的数量随时间变化而有丝分裂期间的数量恒定。尽管在缺乏MztA的细胞中经常观察到异常的纺锤体。定量PALM成像揭示了SPBs蛋白质组成的出乎意料的动态，相间的γ-微管蛋白复合物的数量随时间变化而有丝分裂期间的数量恒定。尽管在缺乏MztA的细胞中经常观察到异常的纺锤体。定量PALM成像揭示了SPBs蛋白质组成的出乎意料的动态，相间的γ-微管蛋白复合物的数量随时间变化而有丝分裂期间的数量恒定。