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- 2018
Single- and/or double-membrane viral factories?DOI: http://dx.doi.org/10.19070/2330-0027-140003e Keywords: n/a Abstract: Once entering the cell host, viruses needs to interact with intracellular membranes in order to build up their replication organelles or factories, resulting in a remodeling of the cell membranes, the hallmark of virus infection. Positive (+) strand RNA viruses represent the largest group of RNA viruses. Among them two different architectures of replication factories (morphotypes) have been described so far, differing mainly in the amount of lipid bilayers they have: one or two [1]. The single membrane morphotype consists in the formation of negatively curved membranes or invaginations towards the lumen of the host organelle, resulting in the formation of vesicles, vacuoles or spherules. This strategy is used by members of the families Nodaviridae, Bromoviridae, Togaviridae and Flaviviridae. The double-membrane morphotype involves the formation of membranes with positive polarity generating vesicles or tubules containing two membranes. These double-sealed structures have been associated with infections of members of the families Coronaviridae, Arteriviridae, Picornaviridae, Caliciviridae, Closteroviridae and Flaviviridae. To our current knowledge the only (+) strand RNA family following both strategies is the is the family Flaviviridae. It seems, however, that members of the same genus within this family follow the same strategy. Thus, members of the genus Flavivirus induce the formation of vesicles at the endoplasmic reticulum (ER), while hepatitis C virus (HCV) –belonging to the genus Hepacivirus-induces the formation of double membrane vesicles (DMVs) that remain connected to their cell source, also ER, through neck-like structures. This family comprises two more genera: Pestivirus and- Pegivirus, from which it still remains to be elucidated how their members remodel the cell membranes upon infection. The formation of membrane invaginations in the host organelles is normally associated with the presence of a pore or opening towards the cytosol, making these organelles as the suitable viral factories for the synthesis of new RNA [2-5]. Indeed the presence of these pores ensures their active role in replication, allowing a flow of nucleotides and newly synthesized RNA, whereas the invagination provides a protected environment, where the RNA can be replicated/stored, while being hidden from the threatening activity of nucleases or the pattern recognition receptors. However the functionality behind the induction of double-layered structures remains to be determined. Protection from cell sensors is already achieved with only a single membrane. Thus, there
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