Distinct roles of two eIF4E isoforms in the germline of Caenorhabditis elegans

• Published in: Journal of cell science
• Main Authors: Huggins, Hayden P, Subash, Jacob S, Stoffel, Hamilton, Henderson, Melissa A, Hoffman, Jenna L, Buckner, David S, Sengupta, Madhu S, Boag, Peter R, Lee, Myon-Hee, Keiper, Brett D
• Format: Journal Article
• Language: English
• Published: England 01-01-2020
• Subjects: eIF4E; Germline sex determination; Polyribosomes/polysomes; Gametogenesis; 4EBP; mRNA translational control
• ISSN: 1477-9137

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 and -3) that bind m7GTP mRNA caps during C. 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, localizes to germ granules but distinct from IFE-1 and PGL-1, and facilitates oocyte growth and viability. This contrasts with the robust expression of IFE-1 in spermatocytes, 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.