Complex #membrane remodeling during #virion assembly of the 30,000 years-old #Mollivirus sibericum (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Complex membrane remodeling during virion assembly of the 30,000 years-old Mollivirus sibericum

E. R. Quemin, S Corroyer-Dulmont, A Baskaran, E Penard, A. D. Gazi, E Christo-Foroux, P Walther, C Abergel, J Krijnse-Locker

DOI: 10.1128/JVI.00388-19

 

ABSTRACT

Cellular membranes ensure functional compartmentalization by dynamic fusion-fission remodeling and are often targeted by viruses during entry, replication, assembly and egress. Nucleocytoplasmic large DNA viruses (NCLDVs) can recruit host-derived open membrane precursors to form their inner viral membrane. Using complementary 3D-electron microscopy techniques including focused-ion beam scanning electron microscopy and electron tomography, we show that the giant Mollivirus sibericum utilizes the same strategy but also displays unique features. Indeed, assembly is specifically triggered by an open cisterna with a flat pole in its center and open curling ends that grow by recruitment of vesicles, never reported for NCLDVs. These vesicles, abundant in the viral factory (VF), are initially closed but open once in close proximity to the open curling ends of the growing viral membrane. The flat pole appears to play a central role during the entire virus assembly process. While additional capsid layers are assembled from it, it also shapes the growing cisterna into immature crescent-like virions and is located opposite to the membrane elongation and closure sites, thereby providing virions with a polarity. In the VF, DNA-associated filaments are abundant and DNA is packed within virions, prior to particle closure. Altogether, our results highlight the complexity of the interaction between giant viruses and their host. Mollivirus assembly relies on the general strategy of vesicle recruitment, opening and shaping by capsid layers similar to all NCLDVs studied until now. However, the specific features of its assembly suggests that the molecular mechanisms for cellular membrane remodeling and persistence are unique.

 

Importance

Since the first giant virus Mimivirus was identified, other giant representatives are isolated regularly around the World and appear to be unique in several aspects. They belong to at least four viral families and the ways they interact with their hosts remain poorly understood. We focused on Mollivirus sibericum, the sole representative of “Molliviridae” which was isolated from a 30,000 years-old permafrost sample, and exhibits spherical virions of complex composition. In particular, we show that (i) assembly is initiated by a unique structure containing a flat pole positioned at the center of an open cisterna; (ii) core packing involves another cisterna-like element seemingly pushing core proteins into particles being assembled; (iii) specific filamentous structures contain the viral genome before packaging. Altogether, our findings increase our understanding on how complex giant viruses interact with their host and provide the foundation for future studies to elucidate the molecular mechanisms of Mollivirus assembly.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Mimivirus; Molliviridae; Mollivirus sibericum.

—–

The analysis of KV #mimivirus major #capsid gene and its transcript highlights a distinct pattern of gene #evolution and splicing among mimiviruses (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

The analysis of KV mimivirus major capsid gene and its transcript highlights a distinct pattern of gene evolution and splicing among mimiviruses

Paulo Victor Miranda Boratto1, Fábio Pio Dornas1, Lorena Christine Ferreira da Silva1,  Rodrigo Araújo Lima Rodrigues1, Graziele Pereira Oliveira1,  Juliana Reis Cortines2,  Betânia Paiva Drumond1 and Jônatas Santos Abrahão1*

Author Affiliations: 1 Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
2 Instituto de Microbiologia Paulo de Góes, Departamento de Virologia – Centro de Ciências da Saúde, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil

 

ABSTRACT

The inclusion of Mimiviridae members in the putative monophyletic NCLDV group is based on genomic and phylogenomic patterns. This shows that, along with other viral families, they share a set of genes known as core or “hallmark genes”, including the major capsid protein (MCP). Although previous studies have suggested that the maturation of mimivirus MCP transcripts is dependent on splicing, there is little information about the processing of this transcript in other mimivirus isolates. In this work, we report the characterization of a new mimivirus isolate, called KV mimivirus. Analysis of the structure, syntheny and phylogenetic relationships of the MCP gene in many mimivirus isolates revealed a remarkable variation at position and types of intronic and exonic regions, even for mimiviruses belonging to the same lineage. In addition, sequencing of KV and APMV MCP transcripts has shown that, inside the family, even related giant viruses may present different ways to process the MCP mRNA. These results contribute to the understanding of the genetic organization and evolution of the MCP gene in mimiviruses.

 

Importance

Mimivirus isolates have been obtained by prospecting studies since 2003. Based on genomic and phylogenomic studies of conserved genes, these viruses have been clustered together with members of six other viral families. Although being an important part of the so called “hallmark genes”, there is little information about the processing and structure of the major capsid protein (MCP) gene in many mimivirus isolates. In this work, we have analyzed the structure, syntheny and phylogenetic relationships of the MCP gene in many mimivirus isolates, showing remarkable variation at position and types of intronic and exonic regions, even for mimiviruses belonging to the same lineage. These results contribute to the understanding of the genetic organization and evolution of the MCP gene in mimiviruses.

 

FOOTNOTES

Jônatas Santos Abrahão, jonatas.abrahao@gmail.com

Copyright © 2017 American Society for Microbiology. All Rights Reserved.

Keywords: Mimivirus.

——

#Marseillevirus in the #Pharynx of a Patient with #Neurologic #Disorders (@CDC_EIDjournal, extract)

[Source: US Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases Journal, full page: (LINK). Extract.]

Volume 22, Number 11—November 2016 / Letter

Marseillevirus in the Pharynx of a Patient with Neurologic Disorders

_____

To the Editor:

Marseilleviridae is a recently described family of giant amebal viruses (1). Although Marseillevirus, its founding member, and subsequently discovered representatives were isolated primarily from environmental water, marseilleviruses have been recovered from humans (2,3). Senegalvirus, a close Marseillevirus relative, was serendipitously isolated from a healthy man’s feces (2). Metagenomics then unexpectedly identified Marseillevirus-related sequences in blood of healthy donors (3), which was confirmed by PCR, fluorescence in situ hybridization, and serologic testing. Further PCR and serologic studies suggested substantial exposure of humans to marseilleviruses (4,5).

(…)

_____

Sarah Aherfi, Philippe Colson, and Didier Raoult

Author affiliations: Aix-Marseille University, Marseille, France; Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, Marseille

Suggested citation for this article: Aherfi S, Colson P, Raoult D. Marseillevirus in the pharynx of a patient with neurologic disorders. Emerg Infect Dis. 2016 Nov [date cited]. http://dx.doi.org/10.3201/eid2211.160189

DOI: 10.3201/eid2211.160189

Keywords: Research; Mimivirus; Marseillevirus; Meningitis.

——-