Ablation of an Ovarian Tumor Family Deubiquitinase Exposes the Underlying Regulation Governing the Plasticity of Cell Cycle Progression in Toxoplasma gondii.
Ablation of an Ovarian Tumor Family Deubiquitinase Exposes the Underlying Regulation Governing the Plasticity of Cell Cycle Progression in Toxoplasma gondii.
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DOI：
10.1128/mbio.01846-17
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发表时间：
2017-11-21
期刊：
影响因子：
6.4
通讯作者：
Sinai AP
中科院分区：
文献类型：
--
作者：
Dhara A;de Paula Baptista R;Kissinger JC;Snow EC;Sinai AP
弓形虫基因组以生命周期阶段依赖的方式编码细胞周期进展的不同结构的能力。中间宿主中的复制通过内源性发生，而分裂生殖和内多源性的混合发生在最终猫科动物宿主的肠道中。在这里，我们描述了弓形虫速殖子中细胞周期调节的卵巢肿瘤（OTU 家族）去泛素酶、弓形虫 OTUD3A（TgOTUD3A；TGGT1_258780）丧失的后果。突变寄生虫并没有表现出有害性，而是表现出适应性优势，超越了野生型。这种表型是由于大约三分之一的 TgOTUD3A 敲除 (TgOTUD3A-KO) 速殖子通过采用在妊娠母亲体内产生 3、4 或 5 个可存活子代（而不是通常的 2 个）的复制策略而表现出与内生发生的偏差。我们建立了这些改变的复制策略背后的机制基础，即中心体复制失调，导致内部和内部之间的化学计量暂时丧失。和外核，导致在获得 2N 倍性和/或有丝分裂和胞质分裂时未能终止 S 期。由此产生的失调表现为从 S 期到有丝分裂 (S/M)（内多生殖样）或 M 期到胞质分裂 (M/C)（分裂样）的正常转变的偏差。值得注意的是，这些不平衡在胞质分裂之前得到纠正，从而产生正常后代。我们的研究结果表明，有关特定细胞周期结构的利用的决定是由泛素介导的机制控制的，该机制依赖于尚未未知的目标的绝对阈值水平。 TgOTUD3A-KO 突变体的分析为 apicomplexan 细胞周期结构可塑性的潜在机制提供了新的见解。弓形虫的复制可以通过 3 种不同的细胞周期结构进行。无性生殖阶段使用内生生殖，而最终猫科动物宿主的裂殖子则使用分裂生殖和内多生殖的混合体。在这里，我们确定，速殖子中卵巢肿瘤（OTU）家族去泛素酶 TgOTUD3A 的破坏会导致控制寄生虫亚群复制策略选择的机制失调。这些改变的细胞周期的机制基础在于二分中心体的独特生物学，该生物学与 TgOTUD3A-KO 突变体中内部和外部中心体核心之间化学计量的瞬时丧失有关。这凸显了泛素介导的调节在细胞周期从细胞核到出芽阶段的转变中的重要性，并为顶端复合体细胞周期组织的调节提供了新的机制见解。
The Toxoplasma genome encodes the capacity for distinct architectures underlying cell cycle progression in a life cycle stage-dependent manner. Replication in intermediate hosts occurs by endodyogeny, whereas a hybrid of schizogony and endopolygeny occurs in the gut of the definitive feline host. Here, we characterize the consequence of the loss of a cell cycle-regulated ovarian tumor (OTU family) deubiquitinase, OTUD3A of Toxoplasma gondii (TgOTUD3A; TGGT1_258780), in T. gondii tachyzoites. Rather than the mutation being detrimental, mutant parasites exhibited a fitness advantage, outcompeting the wild type. This phenotype was due to roughly one-third of TgOTUD3A-knockout (TgOTUD3A-KO) tachyzoites exhibiting deviations from endodyogeny by employing replication strategies that produced 3, 4, or 5 viable progeny within a gravid mother instead of the usual 2. We established the mechanistic basis underlying these altered replication strategies to be a dysregulation of centrosome duplication, causing a transient loss of stoichiometry between the inner and outer cores that resulted in a failure to terminate S phase at the attainment of 2N ploidy and/or the decoupling of mitosis and cytokinesis. The resulting dysregulation manifested as deviations in the normal transitions from S phase to mitosis (S/M) (endopolygeny-like) or M phase to cytokinesis (M/C) (schizogony-like). Notably, these imbalances are corrected prior to cytokinesis, resulting in the generation of normal progeny. Our findings suggest that decisions regarding the utilization of specific cell cycle architectures are controlled by a ubiquitin-mediated mechanism that is dependent on the absolute threshold levels of an as-yet-unknown target(s). Analysis of the TgOTUD3A-KO mutant provides new insights into mechanisms underlying the plasticity of apicomplexan cell cycle architecture. Replication by Toxoplasma gondii can occur by 3 distinct cell cycle architectures. Endodyogeny is used by asexual stages, while a hybrid of schizogony and endopolygeny is used by merozoites in the definitive feline host. Here, we establish that the disruption of an ovarian-tumor (OTU) family deubiquitinase, TgOTUD3A, in tachyzoites results in dysregulation of the mechanism controlling the selection of replication strategy in a subset of parasites. The mechanistic basis for these altered cell cycles lies in the unique biology of the bipartite centrosome that is associated with the transient loss of stoichiometry between the inner and outer centrosome cores in the TgOTUD3A-KO mutant. This highlights the importance of ubiquitin-mediated regulation in the transition from the nuclear to the budding phases of the cell cycle and provides new mechanistic insights into the regulation of the organization of the apicomplexan cell cycle.