Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.
Genetics. 2022 May 5;221(1). doi: 10.1093/genetics/iyac051.
The ubiquitin-mediated degradation of oocyte translational regulatory proteins is a conserved feature of the oocyte-to-embryo transition. In the nematode Caenorhabditis elegans, multiple translational regulatory proteins, including the TRIM-NHL RNA-binding protein LIN-41/Trim71 and the Pumilio-family RNA-binding proteins PUF-3 and PUF-11, are degraded during the oocyte-to-embryo transition. Degradation of each protein requires activation of the M-phase cyclin-dependent kinase CDK-1, is largely complete by the end of the first meiotic division and does not require the anaphase-promoting complex. However, only LIN-41 degradation requires the F-box protein SEL-10/FBW7/Cdc4p, the substrate recognition subunit of an SCF-type E3 ubiquitin ligase. This finding suggests that PUF-3 and PUF-11, which localize to LIN-41-containing ribonucleoprotein particles, are independently degraded through the action of other factors and that the oocyte ribonucleoprotein particles are disassembled in a concerted fashion during the oocyte-to-embryo transition. We develop and test the hypothesis that PUF-3 and PUF-11 are targeted for degradation by the proteasome-associated HECT-type ubiquitin ligase ETC-1/UBE3C/Hul5, which is broadly expressed in C. elegans. We find that several GFP-tagged fusion proteins that are degraded during the oocyte-to-embryo transition, including fusions with PUF-3, PUF-11, LIN-41, IFY-1/Securin, and CYB-1/Cyclin B, are incompletely degraded when ETC-1 function is compromised. However, it is the fused GFP moiety that appears to be the critical determinant of this proteolysis defect. These findings are consistent with a conserved role for ETC-1 in promoting proteasome processivity and suggest that proteasomal processivity is an important element of the oocyte-to-embryo transition during which many key oocyte regulatory proteins are rapidly targeted for degradation.
卵母细胞翻译调节蛋白的泛素介导降解是卵母细胞到胚胎过渡的一个保守特征。在线虫秀丽隐杆线虫中，包括 TRIM-NHL RNA 结合蛋白 LIN-41/Trim71 和 Pumilio 家族 RNA 结合蛋白 PUF-3 和 PUF-11 在内的多种翻译调节蛋白在卵母细胞到胚胎过渡期间被降解。每种蛋白的降解都需要 M 期细胞周期蛋白依赖性激酶 CDK-1 的激活，在第一次减数分裂末期基本完成，并且不需要后期促进复合物。然而，只有 LIN-41 的降解需要 F 框蛋白 SEL-10/FBW7/Cdc4p，即 SCF 型 E3 泛素连接酶的底物识别亚基。这一发现表明，定位于包含 LIN-41 的核糖核蛋白颗粒中的 PUF-3 和 PUF-11 通过其他因素的作用而独立降解，并且在卵母细胞到胚胎过渡期间，卵母细胞核糖核蛋白颗粒以协调的方式解体。我们提出并测试了这样一个假设，即 PUF-3 和 PUF-11 被广泛表达于秀丽隐杆线虫中的蛋白酶体相关 HECT 型泛素连接酶 ETC-1/UBE3C/Hul5 靶向降解。我们发现，在卵母细胞到胚胎过渡期间被降解的几种 GFP 标记融合蛋白，包括与 PUF-3、PUF-11、LIN-41、IFY-1/Securin 和 CYB-1/Cyclin B 的融合蛋白，在 ETC-1 功能受损时不能完全降解。然而，似乎是融合的 GFP 部分是这种蛋白水解缺陷的关键决定因素。这些发现与 ETC-1 在促进蛋白酶体连续性方面的保守作用一致，并表明蛋白酶体连续性是许多关键卵母细胞调节蛋白迅速被靶向降解的卵母细胞到胚胎过渡过程中的一个重要因素。
