Transition through cell cycle phases requires temporal and spatial regulation of gene expression to ensure accurate chromosome duplication and segregation. This regulation involves dynamic reprogramming of gene expression at multiple transcriptional and posttranscriptional levels. In transcriptionally silent oocytes, the CPEB-family of RNAbinding proteins coordinates temporal and spatial translation regulation of stored maternal mRNAs to drive meiotic progression. CPEB1 mediates mRNA localization to the meiotic spindle, which is required to ensure proper chromosome segregation. Temporal translational regulation also takes place in mitosis, where a large repertoire of transcripts are activated or repressed in specific cell cycle phases. However, whether control of localized translation at the spindle is required for mitosis is unclear, as mitotic and acentriolar-meiotic spindles are functionally and structurally different. Furthermore, the large differences in scale-ratio between cell volume and spindle size in oocytes compared to somatic mitotic cells may generate distinct requirements for gene expression compartmentalization in meiosis and mitosis. Here we show that mitotic spindles contain CPE-localized mRNAs and translating ribosomes. Moreover, CPEB1 and CPEB4 localize in the spindles and they may function sequentially in promoting mitotic stage transitions and correct chromosome segregation. Thus, CPEB1 and CPEB4 bind to specific spindle-associated transcripts controlling the expression and/or localization of their encoded factors that, respectively, drive metaphase and anaphase/cytokinesis.

中文翻译：

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CPEB1 和 CPEB4 的 mRNA 纺锤体定位和有丝分裂翻译调节


细胞周期阶段的转变需要基因表达的时间和空间调节，以确保准确的染色体复制和分离。这种调节涉及多个转录和转录后水平的基因表达的动态重编程。在转录沉默的卵母细胞中，RNA 结合蛋白的 CPEB 家族协调储存的母体 mRNA 的时间和空间翻译调节，以驱动减数分裂进程。 CPEB1 介导 mRNA 定位到减数分裂纺锤体，这是确保正确的染色体分离所必需的。时间翻译调节也发生在有丝分裂中，其中大量转录本在特定的细胞周期阶段被激活或抑制。然而，有丝分裂是否需要控制纺锤体的局部翻译尚不清楚，因为有丝分裂和心粒-减数分裂纺锤体在功能和结构上不同。此外，与体细胞有丝分裂细胞相比，卵母细胞的细胞体积和纺锤体大小之间的比例存在巨大差异，可能对减数分裂和有丝分裂中的基因表达区室化产生不同的要求。在这里，我们表明有丝分裂纺锤体含有 CPE 定位的 mRNA 和翻译核糖体。此外，CPEB1和CPEB4定位于纺锤体，它们可能依次发挥促进有丝分裂阶段转变和正确染色体分离的作用。因此，CPEB1和CPEB4与特定的纺锤体相关转录物结合，控制其编码因子的表达和/或定位，分别驱动中期和后期/细胞分裂。