Tsukamoto Tatsuya, Gearhart Micah D, Spike Caroline A, Huelgas-Morales Gabriela, Mews Makaela, Boag Peter R, Beilharz Traude H, Greenstein David
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455.
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
Genetics. 2017 Aug;206(4):2007-2039. doi: 10.1534/genetics.117.203174. Epub 2017 Jun 1.
An extended meiotic prophase is a hallmark of oogenesis. Hormonal signaling activates the CDK1/cyclin B kinase to promote oocyte meiotic maturation, which involves nuclear and cytoplasmic events. Nuclear maturation encompasses nuclear envelope breakdown, meiotic spindle assembly, and chromosome segregation. Cytoplasmic maturation involves major changes in oocyte protein translation and cytoplasmic organelles and is poorly understood. In the nematode , sperm release the major sperm protein (MSP) hormone to promote oocyte growth and meiotic maturation. Large translational regulatory ribonucleoprotein (RNP) complexes containing the RNA-binding proteins OMA-1, OMA-2, and LIN-41 regulate meiotic maturation downstream of MSP signaling. To understand the control of translation during meiotic maturation, we purified LIN-41-containing RNPs and characterized their protein and RNA components. Protein constituents of LIN-41 RNPs include essential RNA-binding proteins, the GLD-2 cytoplasmic poly(A) polymerase, the CCR4-NOT deadenylase complex, and translation initiation factors. RNA sequencing defined messenger RNAs (mRNAs) associated with both LIN-41 and OMA-1, as well as sets of mRNAs associated with either LIN-41 or OMA-1 Genetic and genomic evidence suggests that GLD-2, which is a component of LIN-41 RNPs, stimulates the efficient translation of many LIN-41-associated transcripts. We analyzed the translational regulation of two transcripts specifically associated with LIN-41 which encode the RNA regulators SPN-4 and MEG-1 We found that LIN-41 represses translation of and , whereas OMA-1 and OMA-2 promote their expression. Upon their synthesis, SPN-4 and MEG-1 assemble into LIN-41 RNPs prior to their functions in the embryo. This study defines a translational repression-to-activation switch as a key element of cytoplasmic maturation.
延长的减数分裂前期是卵子发生的一个标志。激素信号激活CDK1/细胞周期蛋白B激酶以促进卵母细胞减数分裂成熟,这涉及细胞核和细胞质事件。细胞核成熟包括核膜破裂、减数分裂纺锤体组装和染色体分离。细胞质成熟涉及卵母细胞蛋白质翻译和细胞质细胞器的重大变化,目前对此了解甚少。在线虫中,精子释放主要精子蛋白(MSP)激素以促进卵母细胞生长和减数分裂成熟。含有RNA结合蛋白OMA-1、OMA-2和LIN-41的大型翻译调节核糖核蛋白(RNP)复合物在MSP信号下游调节减数分裂成熟。为了了解减数分裂成熟过程中的翻译控制,我们纯化了含有LIN-41的RNP,并对其蛋白质和RNA成分进行了表征。LIN-41 RNP的蛋白质成分包括必需的RNA结合蛋白、GLD-2细胞质聚腺苷酸聚合酶、CCR4-NOT去腺苷酸化酶复合物和翻译起始因子。RNA测序确定了与LIN-41和OMA-1相关的信使RNA(mRNA),以及与LIN-41或OMA-1相关的mRNA组。遗传和基因组证据表明,作为LIN-41 RNP成分的GLD-2刺激许多与LIN-41相关转录本的有效翻译。我们分析了与LIN-41特异性相关的两个转录本的翻译调控,这两个转录本编码RNA调节因子SPN-4和MEG-1。我们发现LIN-41抑制 和 的翻译,而OMA-1和OMA-2促进它们的表达。在它们合成后,SPN-4和MEG-1在胚胎中发挥功能之前组装成LIN-41 RNP。这项研究将翻译抑制到激活的转换定义为细胞质成熟的关键要素。