Análise do conjunto de tRNA em Nucleocytoviricota

Abstract

Giant viruses, commonly known as large nucleocytoplasmic DNA viruses (NCLDV), are part of the new phylum established in 2023 by the International Committee on Taxonomy of Viruses (ICTV), the phylum Nucleocytoviricota. The long genomes of giant viruses encode genes involved in the process of protein translation, such as transfer RNA (tRNA) and aminoacyl tRNA synthetases (aaRS). These components were not previously reported in other viruses until the sequencing of the genome of the first giant virus of amoeba, Mimivirus bradfordmassiliense (originally called Acanthamoeba polyphaga Mimivirus - APMV). In the present work, it was possible to study the prevalence of tRNA through a large-scale search for tRNA genes in the genomes groups of giant viruses that infect free-living amoebas. It was found that the seventy sequences deposited in GenBank from isolated viruses, forty-eight of them contained at least one tRNA gene. This distribution was highly present in the Tupanviruses, which have the largest translation apparatus, and the Mimiviruses, a group with a great number of isolates. A considerable diversity was found in the identification of the anticodon, however a tendency among the viruses towards those corresponding mainly to the amino acid leucine more evident. The organization of these tRNA into clusters was analyzed and occurred in viruses with a high number of encoded tRNA, such as Tupanvirus and Yasminevirus. The introns contained in these genes were also evaluated and were detected in thirty-four genomes. It was not possible to build a phylogenetic tree of the tRNA in giant viruses, despite being that, for the most part, the sequences showed a high rate of conservation among the members of the groups to which they belong. The data obtained in this study demonstrates the diversity and complexity of the translation machinery of giant viruses. Further analyses involving other components of the translational apparatus could provide a new overview of this still largely unexplored area of giant virus genomics.