Maternal RNF114 plays critical roles in activation of the early zygotic genome through promoting ubiquitin-mediated degradation of Chromobox protein CBX5

Zygotic genomic activation (ZGA) is a landmark event in the maternal-to-zygotic transition (MZT), and the regulation of ZGA by maternal factors remains to be elucidated. In this study, the depletion of maternal RNF114 led to 2-cell embryos developmental arrest in mice. RNF114 was proven to play an important role in major ZGA using ethynyl uridine (EU) incorporation and transcriptome analysis. To study the underlying mechanism, we performed protein profiling in mature oocytes and found a potential substrate for RNF114, Chromobox protein CBX5, whose ubiquitination and degradation was regulated by RNF114. Furthermore, the overexpression of CBX5 prevented embryonic development and impeded major ZGA. In summary, our study reveals that maternal RNF114, as a ubiquitin E3 ligase, plays a precise role in mediating the degradation of repressive protein CBX5 during MZT, the misregulation of which may impede the appropriate activation of major ZGA in mouse embryos. RNASeq of MII oocytes,1-cell and 2-cell embryos from Rnf114 Mutant/Control mouse合子基因组激活（Zygotic genomic activation, ZGA）是母源-合子转换（maternal-to-zygotic transition, MZT）中的标志性事件，母源因子对ZGA的调控机制仍有待阐明。本研究发现，母源环指蛋白114（RNF114）的缺失会导致小鼠2-细胞胚胎发育阻滞。通过炔尿苷（ethynyl uridine, EU）掺入实验与转录组分析，证实RNF114在主要ZGA进程中发挥关键调控作用。为探究其潜在分子机制，我们对成熟卵母细胞开展蛋白质组分析，发现RNF114的潜在底物——染色盒蛋白CBX5，其泛素化与降解过程受RNF114调控。进一步实验显示，CBX5过表达会阻碍胚胎发育，并抑制主要ZGA的激活。综上，本研究揭示：作为泛素E3连接酶的母源RNF114，在MZT过程中精准介导阻遏性蛋白CBX5的降解；该调控过程的异常可能会阻碍小鼠胚胎中主要ZGA的正常激活。本数据集包含Rnf114突变型与对照型小鼠的MII期卵母细胞、1-细胞胚胎及2-细胞胚胎的RNA测序（RNASeq）数据。