Identification of the augmin complex in the filamentous fungus Aspergillus nidulans.
Identification of the augmin complex in the filamentous fungus Aspergillus nidulans.
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DOI：
10.1371/journal.pone.0101471
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Goshima G
中科院分区：
文献类型：
--
作者：
Edzuka T;Yamada L;Kanamaru K;Sawada H;Goshima G
Augmin是一种与纺锤体微管（MT）结合的蛋白质复合物，募集有效的MT成核剂γ-微管蛋白，从而促进有丝分裂和减数分裂纺锤体内的中心体非依赖性MT产生。Augmin是无中心体纺锤体组装所必需的，这通常在植物有丝分裂和雌性动物减数分裂期间观察到。在许多具有中心体的动物体细胞中，中心体和Augmin依赖的机制协同工作以实现有效的纺锤体组装和胞质分裂。酵母在进化过程中丢失了augmin基因。据推测，他们强大的MT成核从纺锤体极体（SPB），中心体等效的结构在真菌中，弥补了缺乏Augmin。然而，有趣的是，已经在丝状真菌的基因组中发现了与Augmin亚基同源的基因（Aug 6/AUGF），其具有作为稳健的MT成核中心的SPB。在这里，我们的目的是澄清，如果augmin复合物存在于丝状真菌，并确定其在有丝分裂中的作用。通过分析丝状真菌构巢曲霉中的Aug 6样基因，我们发现它与其他几种蛋白质形成了一个大的复合物，这些蛋白质与已知的Augmin亚基具有微弱但重要的同源性。以.在nidulans中，augmin在SPB富集，并且在有丝分裂期间也与纺锤体MT相关。然而，augmin基因破坏剂在正常、检查点缺陷或MT不稳定的条件下并未表现出生长缺陷。此外，我们没有得到任何证据表明A.巢蛋白Augmin在γ-微管蛋白募集或有丝分裂细胞分裂中起作用。我们的研究揭示了真菌物种中Augmin复合物的保守性，并进一步表明Augmin除了有丝分裂纺锤体MT成核外，还有几种功能尚未确定。
Augmin is a protein complex that binds to spindle microtubules (MTs), recruits the potent MT nucleator, γ-tubulin, and thereby promotes the centrosome-independent MT generation within mitotic and meiotic spindles. Augmin is essential for acentrosomal spindle assembly, which is commonly observed during mitosis in plants and meiosis in female animals. In many animal somatic cells that possess centrosomes, the centrosome- and augmin-dependent mechanisms work cooperatively for efficient spindle assembly and cytokinesis. Yeasts have lost the augmin genes during evolution. It is hypothesized that their robust MT nucleation from the spindle pole body (SPB), the centrosome-equivalent structure in fungi, compensates for the lack of augmin. Intriguingly, however, a gene homologous to an augmin subunit (Aug6/AUGF) has been found in the genome of filamentous fungi, which has the SPB as a robust MT nucleation centre. Here, we aimed to clarify if the augmin complex is present in filamentous fungi and to identify its role in mitosis. By analysing the Aug6-like gene in the filamentous fungus Aspergillus nidulans, we found that it forms a large complex with several other proteins that share weak but significant homology to known augmin subunits. In A. nidulans, augmin was enriched at the SPB and also associated with spindle MTs during mitosis. However, the augmin gene disruptants did not exhibit growth defects under normal, checkpoint-deficient, or MT-destabilised conditions. Moreover, we obtained no evidence that A. nidulans augmin plays a role in γ-tubulin recruitment or in mitotic cell division. Our study uncovered the conservation of the augmin complex in the fungal species, and further suggests that augmin has several functions, besides mitotic spindle MT nucleation, that are yet to be identified.
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