The Toxoplasma Centrocone Houses Cell Cycle Regulatory Factors.
The Toxoplasma Centrocone Houses Cell Cycle Regulatory Factors.
复制标题
弓形虫中心酮容纳细胞周期调节因子。
DOI：
10.1128/mbio.00579-17
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发表时间：
2017-08-22
期刊：
影响因子：
6.4
通讯作者：
White MW
中科院分区：
文献类型：
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作者：
Naumov A;Kratzer S;Ting LM;Kim K;Suvorova ES;White MW
我们对顶复门寄生虫细胞周期调控机制的了解非常有限。在这项研究中，我们描述了一种新的弓形虫因子，它在染色体复制和细胞质和核有丝分裂结构的调节中起着至关重要的作用，我们将这种因子命名为ECR 1。ECR 1是通过互补温度敏感（ts）突变体发现的，该突变体在40°C下遭受致命的、不受控制的染色体复制，类似于携带拓扑异构酶缺陷的ts突变体。ECR 1是一种52 kDa的蛋白质，含有不同的RING和TRAF-Sina样锌结合结构域，这些结构域在速殖子细胞周期中动态表达。ECR 1在S期早期首先出现在核膜顶复体（centrocone）的独特纺锤体隔室中，然后在S期晚期出现在核中，在那里它达到最大表达。在核分裂之后，但在子寄生虫与母寄生虫分离之前，ECR 1下调并且在新的子寄生虫中不存在。ECR 1的蛋白质组学鉴定了与泛素介导的蛋白质降解机制和微型染色体维持复合物的相互作用，并且ECR 1的丢失导致该复合物的关键成员MCM 2的稳定性增加。ECR 1还与细胞周期蛋白依赖性激酶（CDK）相关激酶T.弓形虫Crk 5（TgCrk 5），其在速殖子复制期间显示类似的细胞周期表达和定位。重要的是，ECR 1/TgCrk 5在中心锥中的定位表明，这种顶复体特异性纺锤体隔室容纳控制寄生虫细胞周期的重要调节因子。顶复门家族的寄生虫是人类疾病的重要原因，包括疟疾、弓形虫病和隐孢子虫病。寄生虫生长是致病的根本原因，然而，尽管如此重要，寄生虫复制的分子基础知之甚少。填补这一知识空白不能通过挖掘最近的全基因组测序数据来完成，因为顶复门的细胞周期有很大的不同，缺乏许多关键的调控因素，充分研究酵母和哺乳动物细胞分裂模型。我们已经利用正向遗传学发现的必要因素，调节细胞分裂在这些寄生虫使用弓形虫模型。这种方法的一个例子是在这里描述的一个假定的E3连接酶/蛋白激酶机制参与调节染色体复制和有丝分裂过程的无性阶段寄生虫的发现。
Our knowledge of cell cycle regulatory mechanisms in apicomplexan parasites is very limited. In this study, we describe a novel Toxoplasma gondii factor that has a vital role in chromosome replication and the regulation of cytoplasmic and nuclear mitotic structures, and we named this factor ECR1 for essential for chromosome replication 1. ECR1 was discovered by complementation of a temperature-sensitive (ts) mutant that suffers lethal, uncontrolled chromosome replication at 40°C similar to a ts mutant carrying a defect in topoisomerase. ECR1 is a 52-kDa protein containing divergent RING and TRAF-Sina-like zinc binding domains that are dynamically expressed in the tachyzoite cell cycle. ECR1 first appears in the unique spindle compartment of the Apicomplexa (centrocone) of the nuclear envelope in early S phase and then in the nucleus in late S phase where it reaches maximum expression. Following nuclear division, but before daughter parasites separate from the mother parasite, ECR1 is downregulated and is absent in new daughter parasites. The proteomics of ECR1 identified interactions with the ubiquitin-mediated protein degradation machinery and the minichromosome maintenance complex, and the loss of ECR1 led to increased stability of a key member of this complex, MCM2. ECR1 also forms a stable complex with the cyclin-dependent kinase (CDK)-related kinase, T. gondii Crk5 (TgCrk5), which displays a similar cell cycle expression and localization during tachyzoite replication. Importantly, the localization of ECR1/TgCrk5 in the centrocone indicates that this Apicomplexa-specific spindle compartment houses important regulatory factors that control the parasite cell cycle. Parasites of the apicomplexan family are important causes of human disease, including malaria, toxoplasmosis, and cryptosporidiosis. Parasite growth is the underlying cause of pathogenesis, yet despite this importance, the molecular basis for parasite replication is poorly understood. Filling this knowledge gap cannot be accomplished by mining recent whole-genome sequencing data because apicomplexan cell cycles differ substantially and lack many of the key regulatory factors of well-studied yeast and mammalian cell division models. We have utilized forward genetics to discover essential factors that regulate cell division in these parasites using the Toxoplasma gondii model. An example of this approach is described here with the discovery of a putative E3 ligase/protein kinase mechanism involved in regulating chromosome replication and mitotic processes of asexual stage parasites.