Publication Date:
2016-03-05
Description:
Since their discovery, giant viruses have revealed several unique features that challenge the conventional definition of a virus, such as their large and complex genomes, their infection by virophages and their presence of transferable short element transpovirons. Here we investigate the sensitivity of mimivirus to virophage infection in a collection of 59 viral strains and demonstrate lineage specificity in the resistance of mimivirus to Zamilon, a unique virophage that can infect lineages B and C of mimivirus but not lineage A. We hypothesized that mimiviruses harbour a defence mechanism resembling the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas system that is widely present in bacteria and archaea. We performed de novo sequencing of 45 new mimivirus strains and searched for sequences specific to Zamilon in a total of 60 mimivirus genomes. We found that lineage A strains are resistant to Zamilon and contain the insertion of a repeated Zamilon sequence within an operon, here named the 'mimivirus virophage resistance element' (MIMIVIRE). Further analyses of the surrounding sequences showed that this locus is reminiscent of a defence mechanism related to the CRISPR-Cas system. Silencing the repeated sequence and the MIMIVIRE genes restores mimivirus susceptibility to Zamilon. The MIMIVIRE proteins possess the typical functions (nuclease and helicase) involved in the degradation of foreign nucleic acids. The viral defence system, MIMIVIRE, represents a nucleic-acid-based immunity against virophage infection.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Levasseur, Anthony -- Bekliz, Meriem -- Chabriere, Eric -- Pontarotti, Pierre -- La Scola, Bernard -- Raoult, Didier -- England -- Nature. 2016 Mar 10;531(7593):249-52. doi: 10.1038/nature17146. Epub 2016 Feb 29.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Aix-Marseille Universite, Unite de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, Marseille, France. ; IHU Mediterranee Infection, Pole des Maladies Infectieuses, Assistance Publique-Hopitaux de Marseille, Faculte de Medecine, 27 Boulevard Jean Moulin, 13005 Marseille, France. ; Aix-Marseille Universite, CNRS, Centrale Marseille, I2M, UMR7373, FR 4213 - FR Eccorev 3098, equipe EBM, 13331 Marseille, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26934229" target="_blank"〉PubMed〈/a〉
Keywords:
Base Sequence
;
CRISPR-Cas Systems/genetics
;
Chromosomes/genetics
;
DNA Helicases/genetics/metabolism
;
DNA, Viral/genetics/metabolism
;
Deoxyribonucleases/genetics/metabolism
;
Genes, Viral/genetics
;
Genome, Viral/genetics
;
Mimiviridae/classification/enzymology/*genetics/*immunology
;
Operon/genetics
;
Viral Proteins/genetics/metabolism
;
Viruses/genetics/*immunology
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
