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Virus Assembly (virus + assembly)
Selected AbstractsCis -preferential recruitment of duck hepatitis B virus core protein to the RNA/polymerase preassembly complexHEPATOLOGY, Issue 1 2002Fritz von Weizsäcker M.D. Hepadnaviral replication requires the concerted action of the polymerase and core proteins to ensure selective packaging of the RNA pregenome into nucleocapsids. Virus assembly is initiated by cis -preferential binding of polymerase to the encapsidation signal ,, present on pregenomic RNA. Using the duck hepatitis B virus (DHBV) model, we analyzed how core protein is recruited to the RNA/polymerase preassembly complex. Two sets of trans-complementation assays were performed in cotransfected hepatoma cells. First, a replication-competent DHBV construct was tested for its ability to rescue replication of genomes bearing mutations within the core region. Self-packaging of wild-type pregenomes was more efficient than cross-packaging of core-deficient pregenomes, and this bias was strongly enhanced if mutant pregenomes coded for self-assembly,competent, but packaging-deficient, core proteins. Second, the site of wild-type core protein translation, i.e., pregenomic RNA (cis) or separate messenger RNA (trans), was analyzed for its effect on the phenotype of a previously described dominant-negative (DN) DHBV core protein mutant. This mutant forms chimeric nucleocapsids with wild-type core proteins and blocks reverse transcription within most, but not all, mixed particles. Strikingly, suppression of viral DNA synthesis by the mutant increased 100-fold when wild-type core protein was provided in trans. Our results suggest that recruitment of core protein to the DHBV preassembly complex occurs in a cis -preferential manner. This mechanism may account for the leakiness of DN DHBV core protein mutants targeting reverse transcription. [source] The capsid protein of human immunodeficiency virus: intersubunit interactions during virus assemblyFEBS JOURNAL, Issue 21 2009Mauricio G. Mateu 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. [source] Modeling the competition between aggregation and self-assembly during virus-like particle processing,BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Yong Ding Abstract Understanding and controlling aggregation is an essential aspect in the development of pharmaceutical proteins to improve product yield, potency and quality consistency. Even a minute quantity of aggregates may be reactogenic and can render the final product unusable. Self-assembly processing of virus-like particles (VLPs) is an efficient method to quicken the delivery of safe and efficacious vaccines to the market at low cost. VLP production, as with the manufacture of many biotherapeutics, is susceptible to aggregation, which may be minimized through the use of accurate and practical mathematical models. However, existing models for virus assembly are idealized, and do not predict the non-native aggregation behavior of self-assembling viral subunits in a tractable nor useful way. Here we present a mechanistic mathematical model describing VLP self-assembly that accounts for partitioning of reactive subunits between the correct and aggregation pathways. Our results show that unproductive aggregation causes up to 38% product loss by competing favorably with the productive nucleation of self-assembling subunits, therefore limiting the availability of nuclei for subsequent capsid growth. The protein subunit aggregation reaction exhibits an apparent second-order concentration dependence, suggesting a dimerization-controlled agglomeration pathway. Despite the plethora of possible assembly intermediates and aggregation pathways, protein aggregation behavior may be predicted by a relatively simple yet realistic model. More importantly, we have shown that our bioengineering model is amenable to different reactor formats, thus opening the way to rational scale-up strategies for products that comprise biomolecular assemblies. Biotechnol. Bioeng. 2010;107: 550,560. © 2010 Wiley Periodicals, Inc. [source] Measles virus nucleocapsid transport to the plasma membrane requires stable expression and surface accumulation of the viral matrix proteinCELLULAR MICROBIOLOGY, Issue 5 2007Nicole Runkler Summary In measles virus (MV)-infected cells the matrix (M) protein plays a key role in virus assembly and budding processes at the plasma membrane because it mediates the contact between the viral surface glycoproteins and the nucleocapsids. By exchanging valine 101, a highly conserved residue among all paramyxoviral M proteins, we generated a recombinant MV (rMV) from cloned cDNA encoding for a M protein with an increased intracellular turnover. The mutant rMV was barely released from the infected cells. This assembly defect was not due to a defective M binding to other matrix- or nucleoproteins, but could rather be assigned to a reduced ability to associate with cellular membranes, and more importantly, to a defective accumulation at the plasma membrane which was accompanied by the deficient transport of nucleocapsids to the cell surface. Thus, we show for the first time that M stability and accumulation at intracellular membranes is a prerequisite for M and nucleocapsid co-transport to the plasma membrane and for subsequent virus assembly and budding processes. [source] Viral interactions with the cytoskeleton: a hitchhiker's guide to the cellCELLULAR MICROBIOLOGY, Issue 3 2006Kerstin Radtke Summary The actin and microtubule cytoskeleton play important roles in the life cycle of every virus. During attachment, internalization, endocytosis, nuclear targeting, transcription, replication, transport of progeny subviral particles, assembly, exocytosis, or cell-to-cell spread, viruses make use of different cellular cues and signals to enlist the cytoskeleton for their mission. Viruses induce rearrangements of cytoskeletal filaments so that they can utilize them as tracks or shove them aside when they represent barriers. Viral particles recruit molecular motors in order to hitchhike rides to different subcellular sites which provide the proper molecular environment for uncoating, replicating and packaging viral genomes. Interactions between subviral components and cytoskeletal tracks also help to orchestrate virus assembly, release and efficient cell-to-cell spread. There is probably not a single virus that does not use cytoskeletal and motor functions in its life cycle. Being well informed intracellular passengers, viruses provide us with unique tools to decipher how a particular cargo recruits one or several motors, how these are activated or tuned down depending on transport needs, and how cargoes switch from actin tracks to microtubules to nuclear pores and back. [source] Sequence and structure relatedness of matrix protein of human respiratory syncytial virus with matrix proteins of other negative-sense RNA virusesCLINICAL MICROBIOLOGY AND INFECTION, Issue 10 2004K. Latiff Abstract Matrix proteins of viruses within the order Mononegavirales have similar functions and play important roles in virus assembly. Protein sequence alignment, phylogenetic tree derivation, hydropathy profiles and secondary structure prediction were performed on selected matrix protein sequences, using human respiratory syncytial virus matrix protein as the reference. No general conservation of primary, secondary or tertiary structure was found, except for a broad similarity in the hydropathy pattern correlating with the fact that all the proteins studied are membrane-associated. Interestingly, the matrix proteins of Ebola virus and human respiratory syncytial virus shared secondary structure homology. [source] | |||||||||||||