Two zebrafish eIF4E family members are differentially expressed and functionally divergent

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Eukaryotic translation initiation factor 4E (eIF4E) is crucial for cap-dependent mRNA translation.
• Homologous proteins to eIF4E have been identified across various species, forming a distinct protein family.
• The prototypical eIF4E is designated as eIF4E-1.

Purpose of the Study:

• To characterize two novel eIF4E family members in zebrafish (Danio rerio).
• To determine the functional roles and evolutionary origins of these zebrafish eIF4E homologs.

Main Methods:

• Sequence comparison and identity analysis between zebrafish and human eIF4E proteins.
• Expression pattern analysis of zebrafish eIF4E-1A and eIF4E-1B.
• Functional assays including m(7)GTP binding, eIF4G and 4E-BP interaction, and yeast complementation.

Main Results:

• Two zebrafish eIF4E family members, eIF4E-1A (82% identity to human eIF4E-1) and eIF4E-1B (66% identity), were identified.
• eIF4E-1A is ubiquitously expressed and functionally equivalent to human eIF4E-1, binding m(7)GTP, eIF4G, and 4E-BP.
• eIF4E-1B, despite possessing conserved interaction residues, failed to interact with cap structures, eIF4G, or 4E-BPs, suggesting a non-canonical function.

Conclusions:

• Zebrafish eIF4E-1A serves as a functional homolog of human eIF4E-1 in mRNA translation.
• The distinct expression pattern of eIF4E-1B suggests specialized roles beyond canonical translation initiation.
• The identification of these homologs provides insights into the evolution and diversification of the eIF4E family in vertebrates.