The analysis of translation-related gene set boosts debates around origin and evolution of mimiviruses

Abstract

The giant mimiviruses challenged the well-established concept of viruses, blurring the roots of the tree of life, mainly due to their genetic content. Along with other nucleo-cytoplasmic large DNA viruses, they compose a new proposed order—named Megavirales—whose origin and evolution generate heated debate in the scientific community. The presence of an arsenal of genes not widespread in the virosphere related to important steps of the translational process, including transfer RNAs, aminoacyl-tRNA synthetases, and translation factors for peptide synthesis, constitutes an important element of this debate. In this review, we highlight the main findings to date about the translational machinery of the mimiviruses and compare their distribution along the distinct members of the family Mimiviridae. Furthermore, we discuss how the presence and/or absence of the translation-related genes among mimiviruses raises important insights to boost the debate on their origin and evolutionary history.

Translational Control in Virus-Infected Cells

“…RNA structural elements and modifications detected by host sentinel molecules coordinate powerful antiviral responses intended to restrict virus access to the translational apparatus. Further insights can be expected from functional analysis of the genes encoding certain translation system components in giant Acanthamoeba viruses (Abrahão et al 2017;Schultz et al 2017).…”

Conservation and Variability of the AUG Initiation Codon Context in Eukaryotes

“…Recently, a myriad of giant, novel viruses have been discovered that contain substantial sets of translational factors, including eIF1 and eIF2a [50,51]. It would be exciting to investigate whether or not those factors are involved in the host TIS context recognition.…”

Giant viruses with an expanded complement of translation system components

“…Giant virus genomes encode homologs of diverse bacterial and eukaryotic genes, including translation system components, reigniting the debate over the origin of these viruses (4)(5)(6). It has been proposed that giant viruses constitute remnants of ancient cellular life or are derived from an enigmatic fourth domain of life (3,7,8).…”