EIF4E and Interactors from Unicellular Eukaryotes.

Daniela Ross-Kaschitza,Michael Altmann

doi:10.3390/ijms21062170

Daniela Ross-Kaschitza, Michael Altmann

Open Access

https://doi.org/10.3390/ijms21062170

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Abstract

eIF4E, the mRNA cap-binding protein, is well known as a general initiation factor allowing for mRNA-ribosome interaction and cap-dependent translation in eukaryotic cells. In this review we focus on eIF4E and its interactors in unicellular organisms such as yeasts and protozoan eukaryotes. In a first part, we describe eIF4Es from yeast species such as Saccharomyces cerevisiae, Candida albicans, and Schizosaccharomyces pombe. In the second part, we will address eIF4E and interactors from parasite unicellular species—trypanosomatids and marine microorganisms—dinoflagellates. We propose that different strategies have evolved during evolution to accommodate cap-dependent translation to differing requirements. These evolutive “adjustments” involve various forms of eIF4E that are not encountered in all microorganismic species. In yeasts, eIF4E interactors, particularly p20 and Eap1 are found exclusively in Saccharomycotina species such as S. cerevisiae and C. albicans. For protozoan parasites of the Trypanosomatidae family beside a unique cap4-structure located at the 5′UTR of all mRNAs, different eIF4Es and eIF4Gs are active depending on the life cycle stage of the parasite. Additionally, an eIF4E-interacting protein has been identified in Leishmania major which is important for switching from promastigote to amastigote stages. For dinoflagellates, little is known about the structure and function of the multiple and diverse eIF4Es that have been identified thanks to widespread sequencing in recent years.

Highlights

Unicellular eukaryotes consist of many species and have been traditionally characterized as fungi, obligate parasites of animals such as trypasonomatids (e.g., Leishmania and Trypanosoma species) or marine prototrophs and parasites
While canonical eIF4E is required for overall cap-dependent translation, other eIF4Es fulfill specific functions required under different stress conditions such as high temperature, hypoxia, or nutritional restriction
As a simple model we propose, that eIF4E-eIF4G interaction, which is essential for cap-dependent translation [61], is disrupted during initiation and that this interaction is regulated by phosphorylation/ dephosphorylation of eIF4E

Summary

Introduction

Unicellular eukaryotes consist of many species and have been traditionally characterized as fungi (yeasts), obligate parasites of animals such as trypasonomatids (e.g., Leishmania and Trypanosoma species) or marine prototrophs and parasites (such as those defined as dinoflagellates). EIF4E2 shows reduced interaction with eIF4G and it may be required for translation of specific stress mRNAs. As opposed to S. pombe eIF4E1, eIF4E2 does not cross-complement for S. cerevisiae eIF4E [38,43,44].

Results

Conclusion