scholarly journals Identification of Amino Acids Essential for Viral Replication in the HCMV Helicase-Primase Complex

2018 ◽  
Vol 9 ◽  
Author(s):  
Gaetan Ligat ◽  
Sandra Da Re ◽  
Sophie Alain ◽  
Sébastien Hantz
Keyword(s):  
Amino Acids ◽  
Viral Replication ◽  
Primase Complex

scholarly journals Functional Analysis of PA Binding by Influenza A Virus PB1: Effects on Polymerase Activity and Viral Infectivity

2001 ◽  
Vol 75 (17) ◽  
pp. 8127-8136 ◽  
Author(s):  
Daniel R. Perez ◽  
Ruben O. Donis
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Amino Acid ◽  
Viral Replication ◽  
Influenza A Virus ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Influenza Viruses ◽  
Virus Growth ◽  
Transcription And Replication

ABSTRACT Influenza A virus expresses three viral polymerase (P) subunits—PB1, PB2, and PA—all of which are essential for RNA and viral replication. The functions of P proteins in transcription and replication have been partially elucidated, yet some of these functions seem to be dependent on the formation of a heterotrimer for optimal viral RNA transcription and replication. Although it is conceivable that heterotrimer subunit interactions may allow a more efficient catalysis, direct evidence of their essentiality for viral replication is lacking. Biochemical studies addressing the molecular anatomy of the P complexes have revealed direct interactions between PB1 and PB2 as well as between PB1 and PA. Previous studies have shown that the N-terminal 48 amino acids of PB1, termed domain α, contain the residues required for binding PA. We report here the refined mapping of the amino acid sequences within this small region of PB1 that are indispensable for binding PA by deletion mutagenesis of PB1 in a two-hybrid assay. Subsequently, we used site-directed mutagenesis to identify the critical amino acid residues of PB1 for interaction with PA in vivo. The first 12 amino acids of PB1 were found to constitute the core of the interaction interface, thus narrowing the previous boundaries of domain α. The role of the minimal PB1 domain α in influenza virus gene expression and genome replication was subsequently analyzed by evaluating the activity of a set of PB1 mutants in a model reporter minigenome system. A strong correlation was observed between a functional PA binding site on PB1 and P activity. Influenza viruses bearing mutant PB1 genes were recovered using a plasmid-based influenza virus reverse genetics system. Interestingly, mutations that rendered PB1 unable to bind PA were either nonviable or severely growth impaired. These data are consistent with an essential role for the N terminus of PB1 in binding PA, P activity, and virus growth.

scholarly journals A Domain of Herpes Simplex Virus pUL33 Required To Release Monomeric Viral Genomes from Cleaved Concatemeric DNA

2017 ◽  
Vol 91 (20) ◽  
Author(s):  
Kui Yang ◽  
Xiaoqun Dang ◽  
Joel D. Baines
Keyword(s):  
Amino Acids ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Viral Replication ◽  
Dna Cleavage ◽  
Artificial Chromosome ◽  
Viral Dna ◽  
Viral Genomes ◽  
C Terminus ◽  
Simplex Virus

ABSTRACT Monomeric herpesvirus DNA is cleaved from concatemers and inserted into preformed capsids through the actions of the viral terminase. The terminase of herpes simplex virus (HSV) is composed of three subunits encoded by UL15, UL28, and UL33. The UL33-encoded protein (pUL33) interacts with pUL28, but its precise role in the DNA cleavage and packaging reaction is unclear. To investigate the function of pUL33, we generated a panel of recombinant viruses with either deletions or substitutions in the most conserved regions of UL33 using a bacterial artificial chromosome system. Deletion of 11 amino acids (residues 50 to 60 or residues 110 to 120) precluded viral replication, whereas the truncation of the last 10 amino acids from the pUL33 C terminus did not affect viral replication or the interaction of pUL33 with pUL28. Mutations that replaced the lysine at codon 110 and the arginine at codon 111 with alanine codons failed to replicate, and the pUL33 mutant interacted with pUL28 less efficiently. Interestingly, genomic termini of the large (L) and small (S) components were detected readily in cells infected with these mutants, indicating that concatemeric DNA was cleaved efficiently. However, the release of monomeric genomes as assessed by pulsed-field gel electrophoresis was greatly diminished, and DNA-containing capsids were not observed. These results suggest that pUL33 is necessary for one of the two viral DNA cleavage events required to release individual genomes from concatemeric viral DNA. IMPORTANCE This paper shows a role for pUL33 in one of the two DNA cleavage events required to release monomeric genomes from concatemeric viral DNA. This is the first time that such a phenotype has been observed and is the first identification of a function of this protein relevant to DNA packaging other than its interaction with other terminase components.

scholarly journals Impact of Mutations in Highly Conserved Amino Acids of the HIV-1 Gag-p24 and Env-gp120 Proteins on Viral Replication in Different Genetic Backgrounds

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e94240 ◽  
Author(s):  
Yi Liu ◽  
Ushnal Rao ◽  
Jan McClure ◽  
Philip Konopa ◽  
Siriphan Manocheewa ◽  
...  
Keyword(s):  
Amino Acids ◽  
Viral Replication ◽  
Conserved Amino Acids ◽  
Hiv 1

scholarly journals Role of Murine Leukemia Virus Reverse Transcriptase Deoxyribonucleoside Triphosphate-Binding Site in Retroviral Replication and In Vivo Fidelity

2000 ◽  
Vol 74 (22) ◽  
pp. 10349-10358 ◽  
Author(s):  
Elias K. Halvas ◽  
Evguenia S. Svarovskaia ◽  
Vinay K. Pathak
Keyword(s):  
Amino Acids ◽  
Viral Replication ◽  
Reverse Transcriptase ◽  
Binding Site ◽  
Reverse Transcription ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Deoxyribonucleoside Triphosphate ◽  
Murine Leukemia

ABSTRACT Retroviral populations exhibit a high evolutionary potential, giving rise to extensive genetic variation. Error-prone DNA synthesis catalyzed by reverse transcriptase (RT) generates variation in retroviral populations. Structural features within RTs are likely to contribute to the high rate of errors that occur during reverse transcription. We sought to determine whether amino acids within murine leukemia virus (MLV) RT that contact the deoxyribonucleoside triphosphate (dNTP) substrate are important for in vivo fidelity of reverse transcription. We utilized the previously described ANGIE P encapsidating cell line, which expresses the amphotropic MLV envelope and a retroviral vector (pGA-1). pGA-1 expresses the bacterial β-galactosidase gene (lacZ), which serves as a reporter of mutations. Extensive mutagenesis was performed on residues likely to interact with the dNTP substrate, and the effects of these mutations on the fidelity of reverse transcription were determined. As expected, most substitution mutations of amino acids that directly interact with the dNTP substrate significantly reduced viral titers (>10,000-fold), indicating that these residues played a critical role in catalysis and viral replication. However, the D153A and A154S substitutions, which are predicted to affect the interactions with the triphosphate, resulted in statistically significant increases in the mutation rate. In addition, the conservative substitution F155W, which may affect interactions with the base and the ribose, increased the mutation rate 2.8-fold. Substitutions of residues in the vicinity of the dNTP-binding site also resulted in statistically significant decreases in fidelity (1.3- to 2.4-fold). These results suggest that mutations of residues that contact the substrate dNTP can affect viral replication as well as alter the fidelity of reverse transcription.

scholarly journals Determinants of Dengue Virus NS4A Protein Oligomerization

2015 ◽  
Vol 89 (12) ◽  
pp. 6171-6183 ◽  
Author(s):  
Chia Min Lee ◽  
Xuping Xie ◽  
Jing Zou ◽  
Shi-Hua Li ◽  
Michelle Yue Qi Lee ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dengue Virus ◽  
Viral Replication ◽  
Transmembrane Domain ◽  
Antiviral Drug ◽  
Protein Oligomerization ◽  
Dependent Manner ◽  
Wild Type ◽  
Replication Complex ◽  
Host Membrane

ABSTRACTFlavivirus NS4A protein induces host membrane rearrangement and functions as a replication complex component. The molecular details of how flavivirus NS4A exerts these functions remain elusive. Here, we used dengue virus (DENV) as a model to characterize and demonstrate the biological relevance of flavivirus NS4A oligomerization. DENV type 2 (DENV-2) NS4A protein forms oligomers in infected cells or when expressed alone. Deletion mutagenesis mapped amino acids 50 to 76 (spanning the first transmembrane domain [TMD1]) of NS4A as the major determinant for oligomerization, while the N-terminal 50 residues contribute only slightly to the oligomerization. Nuclear magnetic resonance (NMR) analysis of NS4A amino acids 17 to 80 suggests that residues L31, L52, E53, G66, and G67 could participate in oligomerization. Ala substitution for 15 flavivirus conserved NS4A residues revealed that these amino acids are important for viral replication. Among the 15 mutated NS4A residues, 2 amino acids (E50A and G67A) are located within TMD1. Both E50A and G67A attenuated viral replication, decreased NS4A oligomerization, and reduced NS4A protein stability. In contrast, NS4A oligomerization was not affected by the replication-defective mutations (R12A, P49A, and K80A) located outside TMD1.transcomplementation experiments showed that expression of wild-type NS4A alone was not sufficient to rescue the replication-lethal NS4A mutants. However, the presence of DENV-2 replicons could partially restore the replication defect of some lethal NS4A mutants (L26A and K80A), but not others (L60A and E122A), suggesting an unidentified mechanism governing the outcome of complementation in a mutant-dependent manner. Collectively, the results have demonstrated the importance of TMD1-mediated NS4A oligomerization in flavivirus replication.IMPORTANCEWe report that DENV NS4A forms oligomers. Such NS4A oligomerization is mediated mainly through amino acids 50 to 76 (spanning the first transmembrane domain [TMD1]). The biological importance of NS4A oligomerization is demonstrated by results showing that mutations of flavivirus conserved residues (E50A and G67A located within TMD1) reduced the oligomerization and stability of the NS4A protein, leading to attenuated viral replication. A systematic mutagenesis analysis demonstrated that flavivirus conserved NS4A residues are important for DENV replication. A successfultranscomplementation of replication-lethal NS4A mutant virus requires wild-type NS4A in the context of the viral replication complex. The wild-type NS4A protein alone is not sufficient to rescue the replication defect of NS4A mutants. Intriguingly, distinct NS4A mutants yielded different complementation outcomes in the replicon-containing cells. Overall, the study has enhanced our understanding of flavivirus NS4A at the molecular level. The results also suggest that inhibitor blocking of NS4A oligomerization could be explored for antiviral drug discovery.

scholarly journals Characterization of Dengue Virus NS4A and NS4B Protein Interaction

2015 ◽  
Vol 89 (7) ◽  
pp. 3455-3470 ◽  
Author(s):  
Jing Zou ◽  
Xuping Xie ◽  
Qing-Yin Wang ◽  
Hongping Dong ◽  
Michelle Yueqi Lee ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dengue Virus ◽  
Viral Replication ◽  
Transmembrane Domain ◽  
Nmr Analysis ◽  
Replication Complex ◽  
Essential Components ◽  
Infected Cells ◽  
Er Membrane ◽  
In Cells

ABSTRACTFlavivirus replication is mediated by a membrane-associated replication complex where viral membrane proteins NS2A, NS2B, NS4A, and NS4B serve as the scaffold for the replication complex formation. Here, we used dengue virus serotype 2 (DENV-2) as a model to characterize viral NS4A-NS4B interaction. NS4A interacts with NS4B in virus-infected cells and in cells transiently expressing NS4A and NS4B in the absence of other viral proteins. Recombinant NS4A and NS4B proteins directly bind to each other with an estimatedKd(dissociation constant) of 50 nM. Amino acids 40 to 76 (spanning the first transmembrane domain, consisting of amino acids 50 to 73) of NS4A and amino acids 84 to 146 (also spanning the first transmembrane domain, consisting of amino acids 101 to 129) of NS4B are the determinants for NS4A-NS4B interaction. Nuclear magnetic resonance (NMR) analysis suggests that NS4A residues 17 to 80 form two amphipathic helices (helix α1, comprised of residues 17 to 32, and helix α2, comprised of residues 40 to 47) that associate with the cytosolic side of endoplasmic reticulum (ER) membrane and helix α3 (residues 52 to 75) that transverses the ER membrane. In addition, NMR analysis identified NS4A residues that may participate in the NS4A-NS4B interaction. Amino acid substitution of these NS4A residues exhibited distinct effects on viral replication. Three of the four NS4A mutations (L48A, T54A, and L60A) that affected the NS4A-NS4B interaction abolished or severely reduced viral replication; in contrast, two NS4A mutations (F71A and G75A) that did not affect NS4A-NS4B interaction had marginal effects on viral replication, demonstrating the biological relevance of the NS4A-NS4B interaction to DENV-2 replication. Taken together, the study has provided experimental evidence to argue that blocking the NS4A-NS4B interaction could be a potential antiviral approach.IMPORTANCEFlavivirus NS4A and NS4B proteins are essential components of the ER membrane-associated replication complex. The current study systematically characterizes the interaction between flavivirus NS4A and NS4B. Using DENV-2 as a model, we show that NS4A interacts with NS4B in virus-infected cells, in cells transiently expressing NS4A and NS4B proteins, orin vitrowith recombinant NS4A and NS4B proteins. We mapped the minimal regions required for the NS4A-NS4B interaction to be amino acids 40 to 76 of NS4A and amino acids 84 to 146 of NS4B. NMR analysis revealed the secondary structure of amino acids 17 to 80 of NS4A and the NS4A amino acids that may participate in the NS4A-NS4B interaction. Functional analysis showed a correlation between viral replication and NS4A-NS4B interaction, demonstrating the biological importance of the NS4A-NS4B interaction. The study has advanced our knowledge of the molecular function of flavivirus NS4A and NS4B proteins. The results also suggest that inhibitors of the NS4A-NS4B interaction could be pursued for flavivirus antiviral development.

scholarly journals Dephosphorylation of eIF-2α Mediated by the γ134.5 Protein of Herpes Simplex Virus Type 1 Is Required for Viral Response to Interferon but Is Not Sufficient for Efficient Viral Replication

2003 ◽  
Vol 77 (18) ◽  
pp. 10154-10161 ◽  
Author(s):  
Guofeng Cheng ◽  
Kui Yang ◽  
Bin He
Keyword(s):  
Amino Acids ◽  
Herpes Simplex Virus ◽  
Amino Acid ◽  
Herpes Simplex ◽  
Viral Replication ◽  
Virus Type ◽  
Herpes Simplex Virus Type ◽  
Wild Type ◽  
Simplex Virus

ABSTRACT The γ134.5 protein of herpes simplex virus type 1 (HSV-1) functions to block the shutoff of protein synthesis involving double-stranded RNA-dependent protein kinase (PKR). In this process, the γ134.5 protein recruits cellular protein phosphatase 1 (PP1) to form a high-molecular-weight complex that dephosphorylates eIF-2α. Here we show that the γ134.5 protein is capable of mediating eIF-2α dephosphorylation without any other viral proteins. While deletion of amino acids 1 to 52 from the γ134.5 protein has no effect on eIF-2α dephosphorylation, further truncations up to amino acid 146 dramatically reduce the activity of the γ134.5 protein. An additional truncation up to amino acid 188 is deleterious, indicating that the carboxyl-terminal domain alone is not functional. Like wild-type HSV-1, the γ134.5 mutant with a truncation of amino acids 1 to 52 is resistant to interferon, and resistance to interferon is coupled to eIF-2α dephosphorylation. Intriguingly, this mutant exhibits a similar growth defect seen for the γ134.5 null mutant in infected cells. Restoration of the wild-type γ134.5 gene in the recombinant completely reverses the phenotype. These results indicate that eIF-2α dephosphorylation mediated by the γ134.5 protein is required for HSV response to interferon but is not sufficient for viral replication. Additional functions or activities of the γ134.5 protein contribute to efficient viral infection.

scholarly journals Hydrogen Bonding at a Conserved Threonine in Lentivirus Capsid Is Required for Virus Replication

2003 ◽  
Vol 77 (14) ◽  
pp. 8009-8018 ◽  
Author(s):  
Sarah M. Rue ◽  
Jason W. Roos ◽  
L. Mario Amzel ◽  
Janice E. Clements ◽  
Sheila A. Barber
Keyword(s):  
Amino Acids ◽  
Hydrogen Bonding ◽  
Viral Replication ◽  
Virus Replication ◽  
Antiviral Drug ◽  
Hiv Protease ◽  
Virus Infectivity ◽  
Virion Release ◽  
Immunodeficiency Virus ◽  
N Terminus

ABSTRACT The N terminus of the capsid protein (CA) undergoes a considerable conformational change when the human immunodeficiency virus (HIV) protease cleaves it free from the Pr55Gag polyprotein. This rearrangement is thought to facilitate the establishment of specific CA-CA interactions that are required for the formation of the mature viral core. Substitution of amino acids that are critical for this refolding of the N terminus is generally detrimental to virus replication and mature virion core morphology. Here, we identify a conserved threonine in simian immunodeficiency virus (SIV) CA, T(47)CA, that is requisite for viral replication. Replacement of T(47)CA in the infectious viral clone SIVmac239 with amino acids with different hydrogen-bonding capabilities and analysis of the effects of these substitutions at key steps in the viral life cycle demonstrate that hydrogen bonding at this position is important for virus infectivity and virion release. In the HIV-based homology model of the mature SIV CA N terminus presented in this study, T(47)CA forms several hydrogen bonds with a proximal aspartate, D(50)CA. This model, coupled with strong phenotypic similarities between viral substitution mutants of each of these two residues in all of the virological assays described herein, indicates that hydrogen bonding between T(47)CA and D(50)CA is likely required for viral replication. As hydrogen bonding between these two residues is present in HIV CA as well, this interaction presents a potential target for antiviral drug design.

scholarly journals The Epstein-Barr Virus Lytic Transactivator Zta Interacts with the Helicase-Primase Replication Proteins

1998 ◽  
Vol 72 (11) ◽  
pp. 8559-8567 ◽  
Author(s):  
Zhigang Gao ◽  
Anita Krithivas ◽  
Jon E. Finan ◽  
O. John Semmes ◽  
Sifang Zhou ◽  
...  
Keyword(s):  
Amino Acids ◽  
Epstein Barr Virus ◽  
Nuclear Translocation ◽  
Intracellular Localization ◽  
Activation Domain ◽  
Replication Complex ◽  
Barr Virus ◽  
Amino Terminal ◽  
Epstein Barr ◽  
Primase Complex

ABSTRACT The Epstein-Barr virus transactivator Zta triggers lytic gene expression and is essential for replication of the lytic origin, oriLyt. Previous analysis indicated that the Zta activation domain contributed a replication-specific function. We now show that the Zta activation domain interacts with components of the EBV helicase-primase complex. The three helicase-primase proteins BBLF4 (helicase), BSLF1 (primase), and BBLF2/3 (primase-associated factor) were expressed fused to the Myc epitope. When expression plasmids for BBLF4 or BBLF2/3 plus BSLF1 (primase subcomplex) were separately transfected, the proteins localized to the cytoplasm. Interaction between Zta and the components of the helicase-primase complex was tested by examining the ability of Zta to alter the intracellular localization of these proteins. Cotransfection of Zta with Myc-BBLF4 resulted in nuclear translocation of Myc-BBLF4; similarly, cotransfection of Zta with the primase subcomplex led to nuclear translocation of the Myc-BSLF1 and Myc-BBLF2/3 proteins. This relocalization provides evidence for an interaction between Zta and the helicase and Zta and the primase subcomplex. An affinity assay using glutathioneS-transferase–Zta fusion proteins demonstrated that Myc-BBLF4 and Myc-BBLF2/3 plus BSLF1 bound to the Zta activation domain (amino acids 1 to 133). In the nuclear relocalization assay, the amino-terminal 25 amino acids of Zta were required for efficient interaction with the primase subcomplex but not for interaction with BBLF4. Evidence for interaction between oriLyt bound Zta and the helicase-primase complex was obtained in a superactivation assay using an oriLyt-chloramphenicol acetyltransferase (CAT) reporter. Zta activated expression from a CAT reporter containing the complete oriLyt region and regulated by the oriLyt BHLF1 promoter. Cotransfection of the helicase-primase proteins, one of which was fused to a heterologous activation domain, led to Zta-dependent superactivation of CAT expression. This assay also provided evidence for an interaction between the single-stranded DNA binding protein, BALF2, and the Zta-tethered helicase-primase complex. The helicase-primase interaction is consistent with a role for Zta in stabilizing the formation of an origin-bound replication complex.

scholarly journals Reverse Genetics System for a Human Group A Rotavirus

2019 ◽  
Vol 94 (2) ◽  
Author(s):  
Takahiro Kawagishi ◽  
Jeffery A. Nurdin ◽  
Misa Onishi ◽  
Ryotaro Nouda ◽  
Yuta Kanai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Viral Replication ◽  
Reverse Genetics ◽  
Terminal Region ◽  
Wild Type Virus ◽  
Viral Gene ◽  
Group A Rotavirus ◽  
Truncation Mutant ◽  
Group A ◽  
Biological Differences

ABSTRACT Group A rotavirus (RV) is a major cause of acute gastroenteritis in infants and young children worldwide. Recently, we established an entirely plasmid-based reverse genetics system for simian RV strain SA11. Although that system was robust enough to generate reassortant RVs, including human RV gene segments, and enabled better understanding of the biological differences between animal and human RV strains, a complete reverse genetics system for human RV strains is desirable. Here, we established a plasmid-based reverse genetics system for G4P[8] human RV strain Odelia. This technology was used to generate a panel of monoreassortant viruses between human and simian RV strains for all of the 11 gene segments demonstrating full compatibility between human and simian RV strains. Furthermore, we generated recombinant viruses lacking the C-terminal region of the viral nonstructural protein NSP1 and used it to define the biological function of the interaction between NSP1 and its target protein β-transducin repeat-containing protein (β-TrCP) during viral replication. While the NSP1 truncation mutant lacking the C-terminal 13 amino acids displayed lower β-TrCP degradation activity, it replicated as efficiently as the wild-type virus. In contrast, the truncation mutant lacking the C-terminal 166 amino acids of NSP1 replicated poorly, suggesting that the C-terminal region of NSP1 plays critical roles in viral replication. The system reported here will allow generation of engineered recombinant virus harboring desired mutations, increase our understanding of the molecular biology of human RV, and facilitate development of novel therapeutics and vaccines. IMPORTANCE Reverse genetics, an approach used to generate viruses from cloned cDNA, has increased our understanding of virus biology. Worldwide research led to the development of an entirely plasmid-based reverse genetics system for the simian RV laboratory strain. Although the technique allows generation of gene-modified recombinant RVs, biological differences between animal and human RVs mean that reverse genetics systems for human RV strains are still needed. Here, we describe a reverse genetics system for the high-yield human RV strain Odelia, which replicates efficiently and is suitable for in vitro molecular studies. Monoreassortant viruses between simian and human RV strains and NSP1 mutant viruses generated by the rescue system enabled study of the biological functions of viral gene segments. This human RV reverse genetics system will facilitate study of RV biology and development of vaccines and vectors.

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