Role of Viral RNA and Co-opted Cellular ESCRT-I and ESCRT-III Factors in Formation of Tombusvirus Spherules Harboring the Tombusvirus Replicase

Kovalev, Nikolay; Martín, Isabel Fernández de Castro; Pogany, Judit; Barajas, Daniel; Pathak, Kunj B.; Risco, Cristina; Nagy, Peter D.

doi:10.1128/jvi.02775-15

Cited by 53 publications

(59 citation statements)

References 89 publications

(164 reference statements)

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“…We think that such a scenario is unlikely in alphaviruses and have proposed that in wild-type virus, RNA synthesis and spherule formation would be linked (20). A third example of spherule formation is provided by the unrelated tombusviruses, in which RNA also determines spherule size (30).…”

Section: Discussionmentioning

confidence: 99%

Partially Uncleaved Alphavirus Replicase Forms Spherule Structures in the Presence and Absence of RNA Template

Hellström

Kallio

Utt

et al. 2017

J Virol

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Alphaviruses are positive-strand RNA viruses expressing their replicase as a polyprotein, P1234, which is cleaved to four final products, nonstructural proteins nsP1 to nsP4. The replicase proteins together with viral RNA and host factors form membrane invaginations termed spherules, which act as the replication complexes producing progeny RNAs. We have previously shown that the wild-type alphavirus replicase requires a functional RNA template and active polymerase to generate spherule structures. However, we now find that specific partially processed forms of the replicase proteins alone can give rise to membrane invaginations in the absence of RNA or replication. The minimal requirement for spherule formation was the expression of properly cleaved nsP4, together with either uncleaved P123 or with the combination of nsP1 and uncleaved P23. These inactive spherules were morphologically less regular than replication-induced spherules. In the presence of template, nsP1 plus uncleaved P23 plus nsP4 could efficiently assemble active replication spherules producing both negative-sense and positive-sense RNA strands. P23 alone did not have membrane affinity, but could be recruited to membrane sites in the presence of nsP1 and nsP4. These results define the set of viral components required for alphavirus replication complex assembly and suggest the possibility that it could be reconstituted from separately expressed nonstructural proteins. All positive-strand RNA viruses extensively modify host cell membranes to serve as efficient platforms for viral RNA replication. Alphaviruses and several other groups induce protective membrane invaginations (spherules) as their genome factories. Most positive-strand viruses produce their replicase as a polyprotein precursor, which is further processed through precise and regulated cleavages. We show here that specific cleavage intermediates of the alphavirus replicase can give rise to spherule structures in the absence of viral RNA. In the presence of template RNA, the same intermediates yield active replication complexes. Thus, partially cleaved replicase proteins play key roles that connect replication complex assembly, membrane deformation, and the different stages of RNA synthesis.

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Section: Discussionmentioning

confidence: 99%

Partially Uncleaved Alphavirus Replicase Forms Spherule Structures in the Presence and Absence of RNA Template

Hellström

Kallio

Utt

et al. 2017

J Virol

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“…ZIKV infection leads to intracellular ER membrane rearrangements, and likely new membrane production, that give rise to CM, ER invaginations called "spherules," virus assembly and accumulation, and then trafficking of virus through the Golgi. On the basis of similarities to flavivirus and tombusvirus data (Kovalev et al, 2016), we expect that ZIKV-induced cellular modifications facilitate and compartmentalise the viral replication cycle.…”

Section: Discussionmentioning

confidence: 99%

Zika virus induced cellular remodelling

Rossignol

Peters

Connor

et al. 2017

Cellular Microbiology

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Summary Zika virus (ZIKV) has been associated with morbidities such as Guillain-Barré, infant microcephaly, and ocular disease. The spread of this positive-sense, single-stranded RNA virus and its growing public health threat underscore gaps in our understanding of basic ZIKV virology. To advance knowledge of the virus replication cycle within mammalian cells, we use serial section three-dimensional electron tomography to demonstrate the widespread remodeling of intracellular membranes upon infection with ZIKV. We report extensive structural rearrangements of the endoplasmic reticulum and reveal stages of the ZIKV viral replication cycle. Structures associated with RNA genome replication and virus assembly are observed integrated within the endoplasmic reticulum, and we show viruses in transit through the Golgi apparatus for viral maturation, and subsequent cellular egress. This study characterizes in detail the three-dimensional ultrastructural organization of the ZIKV replication cycle stages. Our results show close adherence of the ZIKV replication cycle to the existing flavivirus replication paradigm.

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“…Individual vesicle sizes seem to depend on the size of encapsulated genomic vRNA. For example, vesicles with a diameter of 66 nm are found in the presence of full‐length (4.8 kb) TBSV RNA, whereas smaller 42 nm vesicles are formed in the presence of truncated (0.6 kb) viral RNA (Kovalev et al ., ). The conserved vRNA association with membranes suggests that in plants RNA‐protein transfer might be facilitated by or might directly involve a secretory/exosome delivery route via PD to gain access to neighbouring cells and the vasculature (see Fig.…”

Section: Mode Of Rna Transportmentioning

confidence: 97%

Long distance RNA movement

Kehr¹,

2018

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Contents Summary29I.Introduction29II.Phloem as a conduit for macromolecules30III.Classes of phloem transported RNAs and their function32IV.Mode of RNA transport35V.Conclusions37Acknowledgements37References37 Summary In higher plants, small noncoding RNAs and large messenger RNA (mRNA) molecules are transported between cells and over long distances via the phloem. These large macromolecules are thought to get access to the sugar‐conducting phloem vessels via specialized plasmodesmata (PD). Analyses of the phloem exudate suggest that all classes of RNA molecules, including silencing‐induced RNAs (siRNAs), micro RNAs (miRNAs), transfer RNAs (tRNAs), ribosomal RNA (rRNAs) and mRNAs, are transported via the vasculature to distant tissues. Although the functions of mobile siRNAs and miRNAs as signalling molecules are well established, we lack a profound understanding of mobile mRNA function(s) in recipient cells and tissues, and how they are selected for transport. A surprisingly high number of up to thousands of mRNAs were described in diverse plant species such as cucumber, pumpkin, Arabidopsis and grapevine to move long distances over graft junctions to distinct body parts. In this review, we present an overview of the classes of mobile RNAs, the potential mechanisms facilitating RNA long‐distance transport, and the roles of mobile RNAs in regulating transcription and translation. Furthermore, we address potential function(s) of mobile protein‐encoding mRNAs with respect to their characteristics and evolutionary constraints.

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Role of Viral RNA and Co-opted Cellular ESCRT-I and ESCRT-III Factors in Formation of Tombusvirus Spherules Harboring the Tombusvirus Replicase

Cited by 53 publications

References 89 publications

Partially Uncleaved Alphavirus Replicase Forms Spherule Structures in the Presence and Absence of RNA Template

Partially Uncleaved Alphavirus Replicase Forms Spherule Structures in the Presence and Absence of RNA Template

Zika virus induced cellular remodelling

Long distance RNA movement

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