Codon usage, amino acid usage, transfer RNA and amino-acyl-tRNA synthetases in Mimiviruses

Area of Science:

• Virology
• Genomics
• Molecular Biology

Background:

• Mimiviruses are giant viruses with exceptionally large genomes and particle sizes, infecting phagocytic protists like Acanthamoeba.
• The Mimiviridae family includes diverse lineages, with Mimiviruses being record holders for size.
• Understanding viral gene expression and host-pathogen interactions is crucial for giant virus research.

Purpose of the Study:

• To analyze codon and amino acid usage in mimiviruses.
• To investigate the adaptation of viral transfer RNA (tRNA) and amino acyl-tRNA synthetases to mimivirus genomes.
• To compare viral and host (Acanthamoeba castellanii) codon usage patterns.

Main Methods:

• Comparative analysis of codon and amino acid frequencies in mimivirus genomes.
• Examination of viral tRNA and amino acyl-tRNA synthetase repertoires.
• Correlation analysis between viral genomic composition and codon usage.

Main Results:

• Mimivirus codon and amino acid usage significantly differs from Acanthamoeba castellanii, correlating with their high adenine-thymine (AT) genome content.
• The viral tRNA and amino acyl-tRNA synthetase set is not globally adapted to the virus's codon usage.
• Specific tRNAs, like Leu(TAA)tRNA, may compensate for the AT-rich codons and aid viral replication.
• Early expressed viral genes show nucleotide content better adapted to the host's codon usage.

Conclusions:

• Mimiviruses possess distinct translational machinery and codon usage biases shaped by their AT-rich genomes.
• Viral tRNAs play a role in accommodating unique codon usage, potentially facilitating replication within Acanthamoeba.
• Early viral gene expression strategies may involve adaptation to host translational machinery.