Modulation of the expression of mimivirus-encoded translation-related genes in response to nutrient availability during Acanthamoeba castellanii infection

Abstract

The complexity of giant virus genomes is intriguing, especially the presence of genes encoding components of the protein translation machinery such as transfer RNAs and aminoacyl-tRNA-synthetases; these features are uncommon among other viruses. Although orthologs of these genes are codified by their hosts, one can hypothesize that having these translation-related genes might represent a gain of fitness during infection. Therefore, the aim of this study was to evaluate the expression of translation-related genes by mimivirus during infection of Acanthamoeba castellanii under different nutritional conditions. In silico analysis of amino acid usage revealed remarkable differences between the mimivirus isolates and the A. castellanii host. Relative expression analysis by quantitative PCR revealed that mimivirus was able to modulate the expression of eight viral translation-related genes according to the amoebal growth condition, with a higher induction of gene expression under starvation. Some mimivirus isolates presented differences in translation-related gene expression; notably, polymorphisms in the promoter regions correlated with these differences. Two mimivirus isolates did not encode the tryptophanyl-tRNA in their genomes, which may be linked with low conservation pressure based on amino acid usage analysis. Taken together, our data suggest that mimivirus can modulate the expression of translation-related genes in response to nutrient availability in the host cell, allowing the mimivirus to adapt to different hosts growing under different nutritional conditions.

Niemeyer Virus: A New Mimivirus Group A Isolate Harboring a Set of Duplicated Aminoacyl-tRNA Synthetase Genes

“…This could have been important in facilitating the occurrence of an event of genetic duplication. Finally, the gene duplication of tyrosyl-tRNA synthetase could represent an important advantage for NYMV in the environment since its cognate amino acid ranks highly in the composition of the amino acid usage profile of mimiviruses ( Silva et al, 2015 ). Beyond that, it was demonstrated in another study that apart from the conserved domains presented by aaRSs, which are involved in the process of aminoacylation, these enzymes might also incorporate novel motifs related to new biological functions in different eukaryotic organisms, for example functions related to angiogenic activity, angiostatic activity, and inflammatory response ( Guo et al, 2010 ).…”

“…In order to check the expression of aaRS by NYMV, we selected four genes based on the APMV genome sequence (methionyl, tyrosyl, cysteinyl, and arginyl tRNA synthetases) to evaluate the expression profile of NYMV in comparison with APMV as previously described by Silva et al (2015) . Twenty-four-well plates containing 1 × 10 5 amoeba per well, kept in PAS medium were infected with NYMV and APMV at M.O.I.…”

“…Relative gene expression analyses were performed using the ΔΔCt method and normalized to the expression of 18S ribosomal RNA (18S rDNA) and the viral RNA helicase mRNA and calibrated using the lower value (=1). Statistical analysis and primers sequences were as described by Silva et al (2015) .…”

Translational Control in Virus-Infected Cells

“…3), stimulating elongation, the impact on infection biology remains largely unknown. Finally, expression of prokaryote-like elongation factors encoded by the giant mimivirus changes in response to nutrient availability (Silva et al 2015), hinting that viral translation factors may supplant or supplement those resident in the host.…”

Methanogenic microbial community of the Eastern Paris Basin: Potential for energy production from organic-rich shales

“…To evaluate the OM degradation capacity of these shale-derived consortia, additional microcosms were prepared in 50 ml serum bottles with 24 ml of organic carbon-depleted (OCD) CP1 growth medium (i.e., elimination of acetate, tryptone, and yeast extract; Meslé et al, 2015) 4 g of pulverized organic-rich source rock (from 12 m depth) as the only carbon source, and inoculated with 1 ml (4%) of the acetate-stabilized (CP1 medium) methanogenic consortium. Prior to inoculation, the consortia were washed twice in OCD medium to remove traces of organic carbon from the culture medium.…”