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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 -
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 -
Molecular Plant-microbe Interactions :... Jan 2020Plum pox virus, the agent that causes sharka disease, is among the most important plant viral pathogens, affecting trees across the globe. The fabric of interactions... (Review)
Review
Plum pox virus, the agent that causes sharka disease, is among the most important plant viral pathogens, affecting trees across the globe. The fabric of interactions that the virus is able to establish with the plant regulates its life cycle, including RNA uncoating, translation, replication, virion assembly, and movement. In addition, plant-virus interactions are strongly conditioned by host specificities, which determine infection outcomes, including resistance. This review attempts to summarize the latest knowledge regarding -host interactions, giving a comprehensive overview of their relevance for viral infection and plant survival, including the latest advances in genetic engineering of resistant species.
Topics: Disease Resistance; Host Specificity; Host-Pathogen Interactions; Plant Diseases; Plum Pox Virus; Prunus; Virus Assembly
PubMed: 31454296
DOI: 10.1094/MPMI-07-19-0189-FI -
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 -
Nature Aug 2022Bacteria encode myriad defences that target the genomes of infecting bacteriophage, including restriction-modification and CRISPR-Cas systems. In response, one family of...
Bacteria encode myriad defences that target the genomes of infecting bacteriophage, including restriction-modification and CRISPR-Cas systems. In response, one family of large bacteriophages uses a nucleus-like compartment to protect its replicating genomes by excluding host defence factors. However, the principal composition and structure of this compartment remain unknown. Here we find that the bacteriophage nuclear shell assembles primarily from one protein, which we name chimallin (ChmA). Combining cryo-electron tomography of nuclear shells in bacteriophage-infected cells and cryo-electron microscopy of a minimal chimallin compartment in vitro, we show that chimallin self-assembles as a flexible sheet into closed micrometre-scale compartments. The architecture and assembly dynamics of the chimallin shell suggest mechanisms for its nucleation and growth, and its role as a scaffold for phage-encoded factors mediating macromolecular transport, cytoskeletal interactions, and viral maturation.
Topics: Bacteria; Bacteriophages; Cell Compartmentation; Cryoelectron Microscopy; Viral Proteins; Virus Assembly
PubMed: 35922510
DOI: 10.1038/s41586-022-05013-4 -
Viruses Aug 2020Since the emergence of HIV and AIDS in the early 1980s, the development of safe and effective therapies has accompanied a massive increase in our understanding of the... (Review)
Review
Since the emergence of HIV and AIDS in the early 1980s, the development of safe and effective therapies has accompanied a massive increase in our understanding of the fundamental processes that drive HIV biology. As basic HIV research has informed the development of novel therapies, HIV inhibitors have been used as probes for investigating basic mechanisms of HIV-1 replication, transmission, and pathogenesis. This positive feedback cycle has led to the development of highly effective combination antiretroviral therapy (cART), which has helped stall the progression to AIDS, prolong lives, and reduce transmission of the virus. However, to combat the growing rates of virologic failure and toxicity associated with long-term therapy, it is important to diversify our repertoire of HIV-1 treatments by identifying compounds that block additional steps not targeted by current drugs. Most of the available therapeutics disrupt early events in the replication cycle, with the exception of the protease (PR) inhibitors, which act at the virus maturation step. HIV-1 maturation consists of a series of biochemical changes that facilitate the conversion of an immature, noninfectious particle to a mature infectious virion. These changes include proteolytic processing of the Gag polyprotein by the viral protease (PR), structural rearrangement of the capsid (CA) protein, and assembly of individual CA monomers into hexamers and pentamers that ultimately form the capsid. Here, we review the development and therapeutic potential of maturation inhibitors (MIs), an experimental class of anti-HIV-1 compounds with mechanisms of action distinct from those of the PR inhibitors. We emphasize the key insights into HIV-1 biology and structure that the study of MIs has provided. We will focus on three distinct groups of inhibitors that block HIV-1 maturation: (1) compounds that block the processing of the CA-spacer peptide 1 (SP1) cleavage intermediate, the original class of compounds to which the term MI was applied; (2) CA-binding inhibitors that disrupt capsid condensation; and (3) allosteric integrase inhibitors (ALLINIs) that block the packaging of the viral RNA genome into the condensing capsid during maturation. Although these three classes of compounds have distinct structures and mechanisms of action, they share the ability to block the formation of the condensed conical capsid, thereby blocking particle infectivity.
Topics: Anti-HIV Agents; Capsid; Capsid Proteins; Clinical Trials as Topic; Drug Resistance, Viral; HIV Infections; HIV Integrase; HIV Integrase Inhibitors; HIV-1; Humans; Indazoles; Protein Processing, Post-Translational; Pyridines; RNA, Viral; Succinates; Triterpenes; Viral Genome Packaging; Virus Assembly; Virus Replication
PubMed: 32858867
DOI: 10.3390/v12090940