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Advances in Virus Research 2020Viruses of archaea represent one of the most enigmatic parts of the virosphere. Most of the characterized archaeal viruses infect extremophilic hosts and display... (Review)
Review
Viruses of archaea represent one of the most enigmatic parts of the virosphere. Most of the characterized archaeal viruses infect extremophilic hosts and display remarkable diversity of virion morphotypes, many of which have never been observed among bacteriophages or viruses of eukaryotes. However, recent environmental studies have shown that archaeal viruses are widespread also in moderate ecosystems, where they play an important ecological role by influencing the turnover of microbial communities, with a global impact on the carbon and nitrogen cycles. In this review, we summarize recent advances in understanding the molecular details of virion organization and assembly of archaeal viruses. We start by briefly introducing the 20 officially recognized families of archaeal viruses and then outline the similarities and differences of archaeal virus assembly with the morphogenesis pathways used by bacterial and eukaryotic viruses, and discuss the evolutionary implications of these observations. Generally, the assembly of the icosahedral archaeal viruses closely follows the mechanisms employed by evolutionarily related bacterial and eukaryotic viruses with the HK97 fold and double jelly-roll major capsid proteins, emphasizing the overall conservation of these pathways over billions of years of evolution. By contrast, archaea-specific viruses employ unique virion assembly mechanisms. We also highlight some of the molecular adaptations underlying the stability of archaeal viruses in extreme environments. Despite considerable progress during the past few years, the archaeal virosphere continues to represent one of the least studied parts of the global virome, with many molecular features awaiting to be discovered and characterized.
Topics: Archaea; Archaeal Viruses; Bacteria; Books; Capsid Proteins; Ecosystem; Genome, Viral; Phylogeny; Viral Proteins; Virus Assembly
PubMed: 33837715
DOI: 10.1016/bs.aivir.2020.09.004 -
Viruses Jul 2019The baculovirus nucleocapsid is formed through a rod-like capsid encapsulating a genomic DNA molecule of 80~180 kbp. The viral capsid is a large oligomer composed of... (Review)
Review
The baculovirus nucleocapsid is formed through a rod-like capsid encapsulating a genomic DNA molecule of 80~180 kbp. The viral capsid is a large oligomer composed of many copies of various protein subunits. The assembly of viral capsids is a complex oligomerization process. The timing of expression of nucleocapsid-related proteins, transport pathways, and their interactions can affect the assembly process of preformed capsids. In addition, the selection of viral DNA and the injection of the viral genome into empty capsids are the critical steps in nucleocapsid assembly. This paper reviews the replication and recombination of baculovirus DNA, expression and transport of capsid proteins, formation of preformed capsids, DNA encapsulation, and nucleocapsid formation. This review will provide a basis for further study of the nucleocapsid assembly mechanism of baculovirus.
Topics: Baculoviridae; DNA, Viral; Genome, Viral; Nucleocapsid; Virus Assembly
PubMed: 31266177
DOI: 10.3390/v11070595 -
ELife Dec 2023Nucleotide and force-dependent mechanisms control how the viral genome of lambda bacteriophage is inserted into capsids.
Nucleotide and force-dependent mechanisms control how the viral genome of lambda bacteriophage is inserted into capsids.
Topics: DNA, Viral; Bacteriophage lambda; Capsid; Genome, Viral; Nucleotides; Virus Assembly
PubMed: 38095555
DOI: 10.7554/eLife.94128 -
Trends in Biochemical Sciences May 2021Virion assembly is an important step in the life cycle of all viruses. For viruses of the Flavivirus genus, a group of enveloped positive-sense RNA viruses, the assembly... (Review)
Review
Virion assembly is an important step in the life cycle of all viruses. For viruses of the Flavivirus genus, a group of enveloped positive-sense RNA viruses, the assembly step represents one of the least understood processes in the viral life cycle. While assembly is primarily driven by the viral structural proteins, recent studies suggest that several nonstructural proteins also play key roles in coordinating the assembly and packaging of the viral genome. This review focuses on describing recent advances in our understanding of flavivirus virion assembly, including the intermolecular interactions between the viral structural (capsid) and nonstructural proteins (NS2A and NS2B-NS3), host factors, as well as features of the viral genomic RNA required for efficient flavivirus virion assembly.
Topics: Flavivirus; RNA, Viral; Viral Nonstructural Proteins; Virion; Virus Assembly
PubMed: 33423940
DOI: 10.1016/j.tibs.2020.12.007 -
Proceedings of the National Academy of... Jul 2023HIV-1 assembly occurs at the inner leaflet of the plasma membrane (PM) in highly ordered membrane microdomains. The size and stability of membrane microdomains is...
HIV-1 assembly occurs at the inner leaflet of the plasma membrane (PM) in highly ordered membrane microdomains. The size and stability of membrane microdomains is regulated by activity of the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) that is localized primarily to the inner leaflet of the PM. In this study, we demonstrate that pharmacological inhibition or depletion of nSMase2 in HIV-1-producer cells results in a block in the processing of the major viral structural polyprotein Gag and the production of morphologically aberrant, immature HIV-1 particles with severely impaired infectivity. We find that disruption of nSMase2 also severely inhibits the maturation and infectivity of other primate lentiviruses HIV-2 and simian immunodeficiency virus, has a modest or no effect on nonprimate lentiviruses equine infectious anemia virus and feline immunodeficiency virus, and has no effect on the gammaretrovirus murine leukemia virus. These studies demonstrate a key role for nSMase2 in HIV-1 particle morphogenesis and maturation.
Topics: Animals; Cats; Horses; Mice; HIV-1; Sphingomyelin Phosphodiesterase; Virus Assembly; Lentivirus; Infectious Anemia Virus, Equine
PubMed: 37406093
DOI: 10.1073/pnas.2219475120 -
Advances in Experimental Medicine and... 2024Poxvirus assembly has been an intriguing area of research for several decades. While advancements in experimental techniques continue to yield fresh insights, many... (Review)
Review
Poxvirus assembly has been an intriguing area of research for several decades. While advancements in experimental techniques continue to yield fresh insights, many questions are still unresolved. Large genome sizes of up to 380 kbp, asymmetrical structure, an exterior lipid bilayer, and a cytoplasmic life cycle are some notable characteristics of these viruses. Inside the particle are two lateral bodies and a protein wall-bound-biconcave core containing the viral nucleocapsid. The assembly progresses through five major stages-endoplasmic reticulum (ER) membrane alteration and rupture, crescent formation, immature virion formation, genome encapsidation, virion maturation and in a subset of viruses, additional envelopment of the virion prior to its dissemination. Several large dsDNA viruses have been shown to follow a comparable sequence of events. In this chapter, we recapitulate our understanding of the poxvirus morphogenesis process while reviewing the most recent advances in the field. We also briefly discuss how virion assembly aids in our knowledge of the evolutionary links between poxviruses and other Nucleocytoplasmic Large DNA Viruses (NCLDVs).
Topics: Poxviridae; Virus Assembly; Humans; Genome, Viral; Virion; Animals; Evolution, Molecular; Endoplasmic Reticulum
PubMed: 38801570
DOI: 10.1007/978-3-031-57165-7_3 -
Virology Journal Feb 2021Influenza A virus (IAV) contains a genome with eight single-stranded, negative-sense RNA segments that encode 17 proteins. During its assembly, all eight separate viral... (Review)
Review
Influenza A virus (IAV) contains a genome with eight single-stranded, negative-sense RNA segments that encode 17 proteins. During its assembly, all eight separate viral RNA (vRNA) segments are incorporated into virions in a selective manner. Evidence suggested that the highly selective genome packaging mechanism relies on RNA-RNA or protein-RNA interactions. The specific structures of each vRNA that contribute to mediating the packaging of the vRNA into virions have been described and identified as packaging signals. Abundant research indicated that sequences required for genome incorporation are not series and are varied among virus genotypes. The packaging signals play important roles in determining the virus replication, genome incorporation and genetic reassortment of influenza A virus. In this review, we discuss recent studies on influenza A virus packaging signals to provide an overview of their characteristics and functions.
Topics: Genome, Viral; Humans; Influenza A virus; RNA, Viral; Virus Assembly; Virus Replication
PubMed: 33596956
DOI: 10.1186/s12985-021-01504-4 -
Cell Apr 2024Unlike those of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and ssRNA viruses, the mechanism of genome packaging of dsRNA viruses is poorly understood....
Unlike those of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and ssRNA viruses, the mechanism of genome packaging of dsRNA viruses is poorly understood. Here, we combined the techniques of high-resolution cryoelectron microscopy (cryo-EM), cellular cryoelectron tomography (cryo-ET), and structure-guided mutagenesis to investigate genome packaging and capsid assembly of bluetongue virus (BTV), a member of the Reoviridae family of dsRNA viruses. A total of eleven assembly states of BTV capsid were captured, with resolutions up to 2.8 Å, with most visualized in the host cytoplasm. ATPase VP6 was found underneath the vertices of capsid shell protein VP3 as an RNA-harboring pentamer, facilitating RNA packaging. RNA packaging expands the VP3 shell, which then engages middle- and outer-layer proteins to generate infectious virions. These revealed "duality" characteristics of the BTV assembly mechanism reconcile previous contradictory co-assembly and core-filling models and provide insights into the mysterious RNA packaging and capsid assembly of Reoviridae members and beyond.
Topics: Bluetongue virus; Capsid; Cryoelectron Microscopy; Capsid Proteins; Animals; Viral Genome Packaging; RNA, Viral; Genome, Viral; Virus Assembly; Electron Microscope Tomography; Virion; Models, Molecular; Cell Line; Cricetinae
PubMed: 38614100
DOI: 10.1016/j.cell.2024.03.007 -
Viruses Dec 2021Retroviruses have a very complex and tightly controlled life cycle which has been studied intensely for decades. After a virus enters the cell, it reverse-transcribes... (Review)
Review
Retroviruses have a very complex and tightly controlled life cycle which has been studied intensely for decades. After a virus enters the cell, it reverse-transcribes its genome, which is then integrated into the host genome, and subsequently all structural and regulatory proteins are transcribed and translated. The proteins, along with the viral genome, assemble into a new virion, which buds off the host cell and matures into a newly infectious virion. If any one of these steps are faulty, the virus cannot produce infectious viral progeny. Recent advances in structural and molecular techniques have made it possible to better understand this class of viruses, including details about how they regulate and coordinate the different steps of the virus life cycle. In this review we summarize the molecular analysis of the assembly and maturation steps of the life cycle by providing an overview on structural and biochemical studies to understand these processes. We also outline the differences between various retrovirus families with regards to these processes.
Topics: Capsid; Cryoelectron Microscopy; Genome, Viral; HIV-1; Humans; Models, Molecular; Retroviridae; Virion; Virus Assembly
PubMed: 35062258
DOI: 10.3390/v14010054 -
Viruses Oct 2020One of the most important steps in any viral lifecycle is the production of progeny virions. For retroviruses as well as other viruses, this step is a highly organized... (Review)
Review
One of the most important steps in any viral lifecycle is the production of progeny virions. For retroviruses as well as other viruses, this step is a highly organized process that occurs with exquisite spatial and temporal specificity on the cellular plasma membrane. To facilitate this process, retroviruses encode short peptide motifs, or L domains, that hijack host factors to ensure completion of this critical step. One such cellular machinery targeted by viruses is known as the Endosomal Sorting Complex Required for Transport (ESCRTs). Typically responsible for vesicular trafficking within the cell, ESCRTs are co-opted by the retroviral Gag polyprotein to assist in viral particle assembly and release of infectious virions. This review in the Viruses Special Issue "The 11th International Retroviral Nucleocapsid and Assembly Symposium", details recent findings that shed light on the molecular details of how ESCRTs and the ESCRT adaptor protein ALIX, facilitate retroviral dissemination at sites of viral assembly.
Topics: Endosomal Sorting Complexes Required for Transport; HIV-1; Nucleocapsid; Retroviridae; Ribonucleoproteins; Virus Assembly; Virus Release; gag Gene Products, Human Immunodeficiency Virus
PubMed: 33092109
DOI: 10.3390/v12101188