Germ cells use both positive and negative mRNA translational control to regulate gene expression that drives their differentiation into gametes. mRNA translational control is mediated by RNA-binding proteins, miRNAs and translation initiation factors. We have uncovered the discrete roles of two translation initiation factor eIF4E isoforms (IFE-1, IFE-3) that bind 7-methylguanosine (m7G) mRNA caps during Caenorhabditis elegans germline development. IFE-3 plays important roles in germline sex determination (GSD), where it promotes oocyte cell fate and is dispensable for spermatogenesis. IFE-3 is expressed throughout the germline and localizes to germ granules, but is distinct from IFE-1 and PGL-1, and facilitates oocyte growth and viability. This contrasts with the robust expression in spermatocytes of IFE-1, the isoform that resides within P granules in spermatocytes and oocytes, and promotes late spermatogenesis. Each eIF4E is localized by its cognate eIF4E-binding protein (IFE-1:PGL-1 and IFE-3:IFET-1). IFE-3 and IFET-1 regulate translation of several GSD mRNAs, but not those under control of IFE-1. Distinct mutant phenotypes, in vivo localization and differential mRNA translation suggest independent dormant and active periods for each eIF4E isoform in the germline.

中文翻译：

---

两种 eIF4E 亚型在秀丽隐杆线虫种系中的不同作用。

生殖细胞使用正向和负向 mRNA 翻译控制来调节基因表达，从而驱动其分化为配子。mRNA 翻译控制由 RNA 结合蛋白、miRNA 和翻译起始因子介导。我们发现了两种翻译起始因子 eIF4E 亚型（IFE-1、IFE-3）在秀丽隐杆线虫种系发育过程中与 7-甲基鸟苷 (m7G) mRNA 帽结合的不同作用。IFE-3 在种系性别决定 (GSD) 中发挥着重要作用，它促进卵母细胞的命运，并且对于精子发生来说是必不可少的。IFE-3 在整个种系中表达并定位于胚芽颗粒，但与 IFE-1 和 PGL-1 不同，并且促进卵母细胞生长和活力。这与 IFE-1 在精母细胞中的强烈表达形成鲜明对比，IFE-1 是存在于精母细胞和卵母细胞 P 颗粒内的异构体，可促进晚期精子发生。每个 eIF4E 均由其同源 eIF4E 结合蛋白（IFE-1:PGL-1 和 IFE-3:IFET-1）定位。IFE-3 和 IFET-1 调节多种 GSD mRNA 的翻译，但不调节受 IFE-1 控制的那些。不同的突变表型、体内定位和差异 mRNA 翻译表明种系中每个 eIF4E 同工型具有独立的休眠期和活跃期。