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Viruses Feb 2015Assembly of herpesvirus nucleocapsids shares significant similarities with the assembly of tailed dsDNA bacteriophages; however, important differences exist. A unique... (Review)
Review
Assembly of herpesvirus nucleocapsids shares significant similarities with the assembly of tailed dsDNA bacteriophages; however, important differences exist. A unique feature of herpesviruses is the presence of different mature capsid forms in the host cell nucleus during infection. These capsid forms, referred to as A-, B-, and C-capsids, represent empty capsids, scaffold containing capsids and viral DNA containing capsids, respectively. The C-capsids are the closest in form to those encapsidated into mature virions and are considered precursors to infectious virus. The evidence supporting A- and B-capsids as either abortive forms or assembly intermediates has been lacking. Interaction of specific capsid forms with viral tegument proteins has been proposed to be a mechanism for quality control at the point of nuclear egress of mature particles. Here, we will review the available literature on these capsid forms and present data to debate whether A- and B-capsids play an important or an extraneous role in the herpesvirus life cycle.
Topics: Capsid; Herpesviridae; Macromolecular Substances; Virus Assembly
PubMed: 25730559
DOI: 10.3390/v7030899 -
Viruses May 2023RNA viruses may be monopartite (all genes on one strand), multipartite (two or more strands packaged separately) or segmented (two or more strands packaged together). In...
RNA viruses may be monopartite (all genes on one strand), multipartite (two or more strands packaged separately) or segmented (two or more strands packaged together). In this article, we consider competition between a complete monopartite virus, A, and two defective viruses, D and E, that have complementary genes. We use stochastic models that follow gene translation, RNA replication, virus assembly, and transmission between cells. D and E multiply faster than A when stored in the same host as A or when together in the same host, but they cannot multiply alone. D and E strands are packaged as separate particles unless a mechanism evolves that allows assembly of D + E segmented particles. We show that if defective viruses assemble rapidly into separate particles, the formation of segmented particles is selected against. In this case, D and E spread as parasites of A, and the bipartite D + E combination eliminates A if the transmissibility is high. Alternatively, if defective strands do not assemble rapidly into separate particles, then a mechanism for assembly of segmented particles is selected for. In this case, the segmented virus can eliminate A if transmissibility is high. Conditions of excess protein resources favor bipartite viruses, while conditions of excess RNA resources favor segmented viruses. We study the error threshold behavior that arises when deleterious mutations are introduced. Relative to bipartite and segmented viruses, deleterious mutations favor monopartite viruses. A monopartite virus can give rise to either a bipartite or a segmented virus, but it is unlikely that both will originate from the same virus.
Topics: Viruses; RNA Viruses; Virus Assembly
PubMed: 37243221
DOI: 10.3390/v15051135 -
Physiology (Bethesda, Md.) Aug 2011Assembly and release of human immunodeficiency virus type 1 (HIV-1) particles is mediated by the viral Gag polyprotein precursor. Gag is synthesized in the cytosol and... (Review)
Review
Assembly and release of human immunodeficiency virus type 1 (HIV-1) particles is mediated by the viral Gag polyprotein precursor. Gag is synthesized in the cytosol and rapidly translocates to membrane to orchestrate particle production. The cell biology of HIV-1 Gag trafficking is currently one of the least understood aspects of HIV-1 replication. In this review, we highlight the current understanding of the cellular machinery involved in Gag trafficking and virus assembly.
Topics: HIV-1; Humans; Protein Transport; Virus Assembly; gag Gene Products, Human Immunodeficiency Virus
PubMed: 21841072
DOI: 10.1152/physiol.00051.2010 -
Journal of Dental Research Apr 2009Human papillomaviruses (HPVs) are small dsDNA tumor viruses, which are the etiologic agents of most cervical cancers and are associated with a growing percentage of... (Review)
Review
Human papillomaviruses (HPVs) are small dsDNA tumor viruses, which are the etiologic agents of most cervical cancers and are associated with a growing percentage of oropharyngeal cancers. The HPV capsid is non-enveloped, having a T=7 icosahedral symmetry formed via the interaction among 72 pentamers of the major capsid protein, L1. The minor capsid protein L2 associates with L1 pentamers, although it is not known if each L1 pentamer contains a single L2 protein. The HPV life cycle strictly adheres to the host cell differentiation program, and as such, native HPV virions are only produced in vivo or in organotypic "raft" culture. Research producing synthetic papillomavirus particles--such as virus-like particles (VLPs), papillomavirus-based gene transfer vectors, known as pseudovirions (PsV), and papillomavirus genome-containing quasivirions (QV)--has bypassed the need for stratifying and differentiating host tissue in viral assembly and has allowed for the rapid analysis of HPV infectivity pathways, transmission, immunogenicity, and viral structure.
Topics: Alphapapillomavirus; Humans; Viral Proteins; Virion; Virus Assembly; Virus Replication
PubMed: 19407149
DOI: 10.1177/0022034509333446 -
Journal of Virology Nov 2017The highly conserved cytoplasmic tail of influenza virus glycoprotein hemagglutinin (HA) contains three cysteines, posttranslationally modified by covalently bound fatty...
The highly conserved cytoplasmic tail of influenza virus glycoprotein hemagglutinin (HA) contains three cysteines, posttranslationally modified by covalently bound fatty acids. While viral HA acylation is crucial in virus replication, its physico-chemical role is unknown. We used virus-like particles (VLP) to study the effect of acylation on morphology, protein incorporation, lipid composition, and membrane fusion. Deacylation interrupted HA-M1 interactions since deacylated mutant HA failed to incorporate an M1 layer within spheroidal VLP, and filamentous particles incorporated increased numbers of neuraminidase (NA). While HA acylation did not influence VLP shape, lipid composition, or HA lateral spacing, acylation significantly affected envelope curvature. Compared to wild-type HA, deacylated HA is correlated with released particles with flat envelope curvature in the absence of the matrix (M1) protein layer. The spontaneous curvature of palmitate was calculated by molecular dynamic simulations and was found to be comparable to the curvature values derived from VLP size distributions. Cell-cell fusion assays show a strain-independent failure of fusion pore enlargement among H2 (A/Japan/305/57), H3 (A/Aichi/2/68), and H3 (A/Udorn/72) viruses. In contradistinction, acylation made no difference in the low-pH-dependent fusion of isolated VLPs to liposomes: fusion pores formed and expanded, as demonstrated by the presence of complete fusion products observed using cryo-electron tomography (cryo-ET). We propose that the primary mechanism of action of acylation is to control membrane curvature and to modify HA's interaction with M1 protein, while the stunting of fusion by deacylated HA acting in isolation may be balanced by other viral proteins which help lower the energetic barrier to pore expansion. Influenza A virus is an airborne pathogen causing seasonal epidemics and occasional pandemics. Hemagglutinin (HA), a glycoprotein abundant on the virion surface, is important in both influenza A virus assembly and entry. HA is modified by acylation whose removal abrogates viral replication. Here, we used cryo-electron tomography to obtain three-dimensional images to elucidate a role for HA acylation in VLP assembly. Our data indicate that HA acylation contributes to the capability of HA to bend membranes and to HA's interaction with the M1 scaffold protein during virus assembly. Furthermore, our data on VLP and, by hypothesis, virus suggests that HA acylation, while not critical to fusion pore formation, contributes to pore expansion in a target-dependent fashion.
Topics: Acylation; Animals; Cell Membrane; Dogs; HEK293 Cells; Hemagglutinin Glycoproteins, Influenza Virus; Humans; Influenza A virus; Lipoylation; Madin Darby Canine Kidney Cells; Membrane Fusion; Virion; Virus Assembly; Virus Replication
PubMed: 28794042
DOI: 10.1128/JVI.00947-17 -
The capsid protein of human immunodeficiency virus: intersubunit interactions during virus assembly.The FEBS Journal Nov 2009The capsid protein (CA) of HIV-1 is composed of two domains, the N-terminal domain (NTD) and the C-terminal domain (CTD). During the assembly of the immature HIV-1... (Review)
Review
The capsid protein (CA) of HIV-1 is composed of two domains, the N-terminal domain (NTD) and the C-terminal domain (CTD). During the assembly of the immature HIV-1 particle, both CA domains constitute a part of the Gag polyprotein, which forms a spherical capsid comprising up to 5000 radially arranged, extended subunits. Gag-Gag interactions in the immature capsid are mediated in large part by interactions between CA domains, which are involved in the formation of a lattice of connected Gag hexamers. After Gag proteolysis during virus maturation, the CA protein is released, and approximately 1000-1500 free CA subunits self-assemble into a truncated cone-shaped capsid. In the mature capsid, NTD-NTD and NTD-CTD interfaces are involved in the formation of CA hexamers, and CTD-CTD interfaces connect neighboring hexamers through homodimerization. The CA-CA interfaces involved in the assembly of the immature capsid and those forming the mature capsid are different, at least in part. CA appears to have evolved an extraordinary conformational plasticity, which allows the creation of multiple CA-CA interfaces and the occurrence of CA conformational switches. This minireview focuses on recent structure-function studies of the diverse CA-CA interactions and interfaces involved in HIV-1 assembly. Those studies are leading to a better understanding of molecular recognition events during virus morphogenesis, and are also relevant for the development of anti-HIV drugs that are able to interfere with capsid assembly or disassembly.
Topics: Capsid Proteins; HIV-1; Protein Conformation; Protein Multimerization; Protein Subunits; Virus Assembly
PubMed: 19825044
DOI: 10.1111/j.1742-4658.2009.07313.x -
Journal of Molecular Biology Jul 2011The pressing need to develop antivirals active against resistant strains of HIV-1 has led to efforts to target steps in the virus life cycle other than reverse... (Review)
Review
The pressing need to develop antivirals active against resistant strains of HIV-1 has led to efforts to target steps in the virus life cycle other than reverse transcription and Gag proteolysis. Among those steps are entry, integration, and assembly and/or maturation. Advances in understanding the structural biology of both the immature and the mature forms of the HIV capsid have made it possible to design or discover small molecules and peptides that interfere with both assembly and maturation. Here, we review the current state of the art in assembly and maturation inhibitors.
Topics: Anti-HIV Agents; Capsid Proteins; HIV-1; Humans; Models, Molecular; Virus Assembly
PubMed: 21762804
DOI: 10.1016/j.jmb.2011.03.074 -
Viruses Oct 2011Insects are commonly infected with multiple viruses including those that cause sublethal, asymptomatic, and latent infections. Traditional methods for virus isolation... (Review)
Review
Insects are commonly infected with multiple viruses including those that cause sublethal, asymptomatic, and latent infections. Traditional methods for virus isolation typically lack the sensitivity required for detection of such viruses that are present at low abundance. In this respect, next generation sequencing technologies have revolutionized methods for the discovery and identification of new viruses from insects. Here we review both traditional and modern methods for virus discovery, and outline analysis of transcriptome and small RNA data for identification of viral sequences. We will introduce methods for de novo assembly of viral sequences, identification of potential viral sequences from BLAST data, and bioinformatics for generating full-length or near full-length viral genome sequences. We will also discuss implications of the ubiquity of viruses in insects and in insect cell lines. All of the methods described in this article can also apply to the discovery of viruses in other organisms.
Topics: Animals; Cell Line; Gene Expression Profiling; Genome, Viral; Genomics; High-Throughput Nucleotide Sequencing; Insect Viruses; Insecta; RNA, Viral; Sequence Analysis, DNA; Transcriptome; Virus Assembly
PubMed: 22069519
DOI: 10.3390/v3101849 -
Viruses Jan 2022Several strategies have been developed to fight viral infections, not only in humans but also in animals and plants. Some of them are based on the development of... (Review)
Review
Several strategies have been developed to fight viral infections, not only in humans but also in animals and plants. Some of them are based on the development of efficient vaccines, to target the virus by developed antibodies, others focus on finding antiviral compounds with activities that inhibit selected virus replication steps. Currently, there is an increasing number of antiviral drugs on the market; however, some have unpleasant side effects, are toxic to cells, or the viruses quickly develop resistance to them. As the current situation shows, the combination of multiple antiviral strategies or the combination of the use of various compounds within one strategy is very important. The most desirable are combinations of drugs that inhibit different steps in the virus life cycle. This is an important issue especially for RNA viruses, which replicate their genomes using error-prone RNA polymerases and rapidly develop mutants resistant to applied antiviral compounds. Here, we focus on compounds targeting viral structural capsid proteins, thereby inhibiting virus assembly or disassembly, virus binding to cellular receptors, or acting by inhibiting other virus replication mechanisms. This review is an update of existing papers on a similar topic, by focusing on the most recent advances in the rapidly evolving research of compounds targeting capsid proteins of RNA viruses.
Topics: Antiviral Agents; Capsid Proteins; Humans; RNA Virus Infections; RNA Viruses; Virus Assembly; Virus Replication
PubMed: 35215767
DOI: 10.3390/v14020174 -
Journal of Virology Aug 2017Chronic hepatitis B virus (HBV) infection is a global public health problem. Although the currently approved medications can reliably reduce the viral load and prevent...
Chronic hepatitis B virus (HBV) infection is a global public health problem. Although the currently approved medications can reliably reduce the viral load and prevent the progression of liver diseases, they fail to cure the viral infection. In an effort toward discovery of novel antiviral agents against HBV, a group of benzamide (BA) derivatives that significantly reduced the amount of cytoplasmic HBV DNA were discovered. The initial lead optimization efforts identified two BA derivatives with improved antiviral activity for further mechanistic studies. Interestingly, similar to our previously reported sulfamoylbenzamides (SBAs), the BAs promote the formation of empty capsids through specific interaction with HBV core protein but not other viral and host cellular components. Genetic evidence suggested that both SBAs and BAs inhibited HBV nucleocapsid assembly by binding to the heteroaryldihydropyrimidine (HAP) pocket between core protein dimer-dimer interfaces. However, unlike SBAs, BA compounds uniquely induced the formation of empty capsids that migrated more slowly in native agarose gel electrophoresis from A36V mutant than from the wild-type core protein. Moreover, we showed that the assembly of chimeric capsids from wild-type and drug-resistant core proteins was susceptible to multiple capsid assembly modulators. Hence, HBV core protein is a dominant antiviral target that may suppress the selection of drug-resistant viruses during core protein-targeting antiviral therapy. Our studies thus indicate that BAs are a chemically and mechanistically unique type of HBV capsid assembly modulators and warranted for further development as antiviral agents against HBV. HBV core protein plays essential roles in many steps of the viral replication cycle. In addition to packaging viral pregenomic RNA (pgRNA) and DNA polymerase complex into nucleocapsids for reverse transcriptional DNA replication to take place, the core protein dimers, existing in several different quaternary structures in infected hepatocytes, participate in and regulate HBV virion assembly, capsid uncoating, and covalently closed circular DNA (cccDNA) formation. It is anticipated that small molecular core protein assembly modulators may disrupt one or multiple steps of HBV replication, depending on their interaction with the distinct quaternary structures of core protein. The discovery of novel core protein-targeting antivirals, such as benzamide derivatives reported here, and investigation of their antiviral mechanism may lead to the identification of antiviral therapeutics for the cure of chronic hepatitis B.
Topics: Anti-HIV Agents; Benzamides; Capsid; Drug Discovery; Drug Evaluation, Preclinical; Hepatitis B virus; Protein Binding; Virus Assembly
PubMed: 28566379
DOI: 10.1128/JVI.00519-17