Elaswad Mohamed T, Gao Mingze, Tice Victoria E, Bright Cora G, Thomas Grace M, Munderloh Chloe, Trombley Nicholas J, Haddad Christya N, Johnson Ulysses G, Cichon Ashley N, Schisa Jennifer A
bioRxiv. 2024 Jul 4:2024.07.01.601596. doi: 10.1101/2024.07.01.601596.
The regulation of maternal mRNAs is essential for proper oogenesis, the production of viable gametes, and to avoid birth defects and infertility. Many oogenic RNA-binding proteins have been identified with roles in mRNA metabolism, some of which localize to dynamic ribonucleoprotein granules and others that appear dispersed. Here, we use a combination of condensation assays and the oogenesis model to determine the intrinsic properties of the conserved KH-domain MEX-3 protein and to identify novel regulators of MEX-3 and the Lsm protein, CAR-1. We demonstrate that MEX-3 undergoes liquid-liquid phase separation and appears to have intrinsic gel-like properties . We also identify novel roles for the CCT chaperonin and actin in preventing ectopic RNA-binding protein condensates in maturing oocytes that appear to be independent of MEX-3 folding. CCT and actin also oppose the expansion of ER sheets that may promote ectopic condensation of RNA-binding proteins that are associated with de-repression of maternal mRNA. This regulatory network is essential to preserve oocyte quality, prevent infertility, and may have implications for understanding the role of hMex3 phase transitions in cancer.
The molecular mechanisms that regulate phase transitions of oogenic RNA-binding proteins are critical to elucidate but are not fully understood.We identify novel regulators of RNA-binding protein phase transitions in maturing oocytes that are required to maintain translational repression of maternal mRNAs and oocyte quality.This study is the first to elucidate a regulatory network involving the CCT chaperonin, actin, and the ER for phase transitions of RNA-binding proteins during oogenesis. Our findings for the conserved MEX-3 protein may also be applicable to better understanding the role of hMex3 phase transitions in cancer.
母体mRNA的调控对于正常的卵子发生、产生有活力的配子以及避免出生缺陷和不孕至关重要。许多卵子发生相关的RNA结合蛋白已被鉴定出在mRNA代谢中发挥作用，其中一些定位于动态核糖核蛋白颗粒，另一些则呈分散状态。在这里，我们结合凝聚分析和卵子发生模型，以确定保守的KH结构域MEX-3蛋白的内在特性，并鉴定MEX-3和Lsm蛋白CAR-1的新型调节因子。我们证明MEX-3经历液-液相分离，并似乎具有内在的凝胶样特性。我们还确定了伴侣蛋白CCT和肌动蛋白在防止成熟卵母细胞中异位RNA结合蛋白凝聚方面的新作用，这似乎与MEX-3折叠无关。CCT和肌动蛋白还对抗内质网片层的扩张，内质网片层的扩张可能促进与母体mRNA去抑制相关的RNA结合蛋白的异位凝聚。这个调控网络对于维持卵母细胞质量、预防不孕至关重要，可能对理解hMex3相变在癌症中的作用具有启示意义。
调节卵子发生相关RNA结合蛋白相变的分子机制至关重要，但尚未完全了解。我们鉴定了成熟卵母细胞中RNA结合蛋白相变的新型调节因子，这些调节因子是维持母体mRNA的翻译抑制和卵母细胞质量所必需的。本研究首次阐明了一个涉及伴侣蛋白CCT、肌动蛋白和内质网的调控网络，该网络参与卵子发生过程中RNA结合蛋白的相变。我们对保守的MEX-3蛋白的研究结果也可能有助于更好地理解hMex3相变在癌症中的作用。
