bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutation of the YXXL Endocytosis Motif in the Cytoplasmic Tail of Pseudorabies Virus gE
Authors: Tirabassi R. S. , Enquist L. W. 
Published: December 2019

ABSTRACTThe role of alphaherpesvirus membrane protein internalization during the course of viral infection remains a matter of speculation. To determine the role of internalization of the pseudorabies virus (PRV) gE and gI proteins, we constructed viral mutants encoding specific mutations in the cytoplasmic tail of the gE gene that inhibited internalization of the gE-gI complex. We used these mutants to assess the role of gE-gI endocytosis in incorporation of the proteins into the viral envelope and in gE-mediated spread or gE-promoted virulence. In addition, we report that another viral mutant, PRV 25, which encodes a gE protein defective in endocytosis, contains an additional, previously uncharacterized mutation in the gE gene. We compared PRV 25 to another viral mutant, PRV 107, that does not express the cytoplasmic tail of the gE protein. The gE protein encoded by PRV 107 is also defective in endocytosis. We conclude that efficient endocytosis of gE is not required for gE incorporation into virions, gE-mediated virulence, or spread of virus in the rat central nervous system. However, we do correlate the defect in endocytosis to a small-plaque phenotype in cultured cells.
The Herpes Simplex Virus Type 1 Regulatory Protein ICP27 Is Required for the Prevention of Apoptosis in Infected Human Cells
Authors: Aubert Martine , Blaho John A. 
Published: December 2019

ABSTRACT
The herpes simplex virus type 1 (HSV-1) ICP27 protein is an immediate-early or α protein which is essential for the optimal expression of late genes as well as the synthesis of viral DNA in cultures of Vero cells. Our specific goal was to characterize the replication of a virus incapable of synthesizing ICP27 in cultured human cells. We found that infection with an HSV-1 ICP27 deletion virus of at least three separate strains of human cells did not produce immediate-early or late proteins at the levels observed following wild-type virus infections. Cell morphology, chromatin condensation, and genomic DNA fragmentation measurements demonstrated that the human cells died by apoptosis after infection with the ICP27 deletion virus. These features of the apoptosis were identical to those which occur during wild-type infections of human cells when total protein synthesis has been inhibited. Vero cells infected with the ICP27 deletion virus did not exhibit any of the features of apoptosis. Based on these results, we conclude that while HSV-1 infection likely induced apoptosis in all cells, viral evasion of the response differed among the cells tested in this study.
The Ski7 Antiviral Protein Is an EF1-α Homolog That Blocks Expression of Non-Poly(A) mRNA in
Saccharomyces cerevisiae
Authors: Benard Lionel , Carroll Kathleen , Valle Rosaura C. P. , Masison Daniel C. , Wickner Reed B. 
Published: December 2019

ABSTRACT

We mapped and cloned
SKI7
, a gene that negatively controls the copy number of L-A and M double-stranded RNA viruses in
Saccharomyces cerevisiae
. We found that it encodes a nonessential 747-residue protein with similarities to two translation factors, Hbs1p and EF1-α. The
ski7
mutant was hypersensitive to hygromycin B, a result also suggesting a role in translation. The
SKI7
product repressed the expression of nonpolyadenylated [non-poly(A)] mRNAs, whether capped or uncapped, thus explaining why Ski7p inhibits the propagation of the yeast viruses, whose mRNAs lack poly(A). The dependence of the Ski7p effect on 3′ RNA structures motivated a study of the expression of capped non-poly(A) luciferase mRNAs containing 3′ untranslated regions (3′UTRs) differing in length. In a wild-type strain, increasing the length of the 3′UTR increased luciferase expression due to both increased rates and duration of translation. Overexpression of Ski7p efficiently cured the satellite virus M
2
due to a twofold-increased repression of non-poly(A) mRNA expression. Our experiments showed that Ski7p is part of the Ski2p-Ski3p-Ski8p antiviral system because a single
ski7
mutation derepresses the expression of non-poly(A) mRNA as much as a quadruple
ski2 ski3 ski7 ski8
mutation, and the effect of the overexpression of Ski7p is not obtained unless other
SKI
genes are functional.
ski1/xrn1Δ ski2Δ
and
ski1/xrn1Δ ski7Δ
mutants were viable but temperature sensitive for growth.
Gibbon Ape Leukemia Virus Receptor Functions of Type III Phosphate Transporters from CHOK1 Cells Are Disrupted by Two Distinct Mechanisms
Authors: Chaudry G. Jilani , Farrell Karen B. , Ting Yuan-Tsang , Schmitz Christian , S. Lie Yolanda , Petropoulos Christos J. , Eiden Maribeth V. 
Published: December 2019

ABSTRACT
The Chinese hamster cell lines E36 and CHOK1 dramatically differ in susceptibility to amphotropic murine leukemia virus (A-MuLV) and gibbon ape leukemia virus (GALV); E36 cells are highly susceptible to both viruses, CHOK1 cells are not. We have previously shown that GALV can infect E36 cells by using both its own receptor, HaPit1, and the A-MuLV receptor, HaPit2. Given that the two cell lines are from the same species, the loss of function of both of these receptors in CHOK1 cells is surprising. Other studies have shown that CHOK1 cells secrete proteins that block A-MuLV entry into CHOK1 as well as E36, suggesting the two A-MuLV receptors are functionally identical. However, CHOK1 conditioned medium does not block GALV entry into E36, indicating the secreted inhibitors do not block HaPit1. HaPit1 and ChoPit1 therefore differ as receptors for GALV; ChoPit1 is either inactivated by secreted factors or intrinsically nonfunctional. To determine why GALV cannot infect CHOK1, we cloned and sequenced ChoPit1 and ChoPit2. ChoPit2 is almost identical to HaPit2, which explains why CHOK1 conditioned medium blocks A-MuLV entry via both receptors. Although ChoPit1 and HaPit1 are 91% identical, a notable difference is at position 550 in the fourth extracellular region, shown by several studies to be crucial for GALV infection. Pit1 and HaPit1 have aspartate at 550, whereas ChoPit1 has threonine at this position. We assessed the significance of this difference for GALV infection by replacing the aspartate 550 in Pit1 with threonine. This single substitution rendered Pit1 nonfunctional for GALV and suggests that threonine at 550 inactivates ChoPit1 as a GALV receptor. Whether native ChoPit1 functions for GALV was determined by interference assays using Lec8, a glycosylation-deficient derivative of CHOK1 that is susceptible to both viruses and that has the same receptors as CHOK1. Unlike with E36, GALV and A-MuLV exhibited reciprocal interference when infecting Lec8, suggesting that they use the same receptor. We conclude both viruses can use ChoPit2 in the absence of the inhibitors secreted by CHOK1 and ChoPit1 is nonfunctional.
Sequence and Genomic Analysis of a Rhesus Macaque Rhadinovirus with Similarity to Kaposi’s Sarcoma-Associated Herpesvirus/Human Herpesvirus 8
Authors: Searles Robert P. , Bergquam Eric P. , Axthelm Michael K. , Wong Scott W. 
Published: December 2019

ABSTRACT
We have sequenced the long unique region (LUR) and characterized the terminal repeats of the genome of a rhesus rhadinovirus (RRV), strain 17577. The LUR as sequenced is 131,364 bp in length, with a G+C content of 52.2% and a CpG ratio of 1.11. The genome codes for 79 open reading frames (ORFs), with 67 of these ORFs similar to genes found in both Kaposi’s sarcoma-associated herpesvirus (KSHV) (formal name, human herpesvirus 8) and herpesvirus saimiri. Eight of the 12 unique genes show similarity to genes found in KSHV, including genes for viral interleukin-6, viral macrophage inflammatory protein, and a family of viral interferon regulatory factors (vIRFs). Genomic organization is essentially colinear with KSHV, the primary differences being the number of cytokine and IRF genes and the location of the gene for dihydrofolate reductase. Highly repetitive sequences are located in positions corresponding to repetitive sequences found in KSHV. Phylogenetic analysis of several ORFs supports the similarity between RRV and KSHV. Overall, the sequence, structural, and phylogenetic data combine to provide strong evidence that RRV 17577 is the rhesus macaque homolog of KSHV.
Production and Characterization of a Soluble, Active Form of Tva, the Subgroup A Avian Sarcoma and Leukosis Virus Receptor
Authors: Balliet John W. , Berson Joanne , D’Cruz Celina M. , Huang Julie , Crane Joanne , Gilbert Joanna M. , Bates Paul 
Published: December 2019

ABSTRACT
The receptor for the subgroup A avian sarcoma and leukosis viruses [ASLV(A)] is the cellular glycoprotein Tva. A soluble form of Tva, sTva, was produced and purified with a baculovirus expression system. Using this system, 7 to 10 mg of purified sTva per liter of cultured Sf9 cells was obtained. Characterization of the carbohydrate modification of sTva revealed that the three N glycosylation sites in sTva were differentially utilized; however, the O glycosylation common to Tva produced in mammalian and avian cells was not observed. Purified sTva demonstrates significant biological activity, specifically blocking infection of avian cells by ASLV(A) with a 90% inhibitory concentration of ∼25 pM. A quantitative enzyme-linked immunosorbent assay, developed to assess the binding of sTva to ASLV envelope glycoprotein, demonstrates that sTva has a high affinity for EnvA, with an apparent dissociation constant of approximately 0.3 nM. Once they are bound, a very stable complex is formed between EnvA and sTva, with an estimated complex half-life of 6 h. The soluble receptor protein described here represents a valuable tool for analysis of the receptor-envelope glycoprotein interaction and for structural analysis of Tva.
Dissecting the Role of the N-Terminal Domain of Human Immunodeficiency Virus Integrase by
trans
-Complementation Analysis
Authors: van den Ent Fusinita M. I. , Vos Arnold , Plasterk Ronald H. A. 
Published: December 2019

ABSTRACT

The human immunodeficiency virus (HIV) integrase protein (IN) catalyzes two reactions required to integrate HIV DNA into the human genome: 3′ processing of the viral DNA ends and integration. IN has three domains, the N-terminal zinc-binding domain, the catalytic core, and the C-terminal SH3 domain. Previously, it was shown that IN proteins mutated in different domains could complement each other. We now report that this does not require any overlap between the two complementing proteins; an N-terminal domain, provided in
trans
, can restore IN activity of a mutant lacking this domain. Only the zinc-coordinating form of the N-terminal domain can efficiently restore IN activity of an N-terminal deletion mutant. This suggests that interaction between different domains of IN is needed for functional multimerization. We find that the N-terminal domain of feline immunodeficiency virus IN can support IN activity of an N-terminal deletion mutant of HIV type 2 IN. These cross-complementation experiments indicate that the N-terminal domain contributes to the recognition of specific viral DNA ends.
Mutational Analysis of Vpr-Induced G
2
Arrest, Nuclear Localization, and Cell Death in Fission Yeast
Authors: Chen Mingzhong , Elder Robert T. , Yu Min , O’Gorman Maurice G. , Selig Luc , Benarous Richard , Yamamoto Ayumu , Zhao Yuqi 
Published: December 2019

ABSTRACT

Cell cycle G
2
arrest, nuclear localization, and cell death induced by human immunodeficiency virus type 1 Vpr were examined in fission yeast by using a panel of Vpr mutations that have been studied previously in human cells. The effects of the mutations on Vpr functions were highly similar between fission yeast and human cells. Consistent with mammalian cell studies, induction of cell cycle G
2
arrest by Vpr was found to be independent of nuclear localization. In addition, G
2
arrest was also shown to be independent of cell killing, which only occurred when the mutant Vpr localized to the nucleus. The C-terminal end of Vpr is crucial for G
2
arrest, the N-terminal α-helix is important for nuclear localization, and a large part of the Vpr protein is responsible for cell killing. It is evident that the overall structure of Vpr is essential for these cellular effects, as N- and C-terminal deletions affected all three cellular functions. Furthermore, two single point mutations (H33R and H71R), both of which reside at the end of each α-helix, disrupted all three Vpr functions, indicating that these two mutations may have strong effects on the overall Vpr structure. The similarity of the mutant effects on Vpr function in fission yeast and human cells suggests that fission yeast can be used as a model system to evaluate these Vpr functions in naturally occurring viral isolates.
Comparison of Immunity Generated by Nucleic Acid-, MF59-, and ISCOM-Formulated Human Immunodeficiency Virus Type 1 Vaccines in Rhesus Macaques: Evidence for Viral Clearance
Authors: Verschoor Ernst J. , Mooij Petra , Oostermeijer Herman , van der Kolk Mike , ten Haaft Peter , Verstrepen Babs , Sun Yide , Morein Bror , Åkerblom Lennart , Fuller Deborah H. , Barnett Susan W. , Heeney Jonathan L. 
Published: December 2019

ABSTRACTThe kinetics of T-helper immune responses generated in 16 mature outbred rhesus monkeys (Macaca mulatta) within a 10-month period by three different human immunodeficiency virus type 1 (HIV-1) vaccine strategies were compared. Immune responses to monomeric recombinant gp120SF2(rgp120) when the protein was expressed in vivo by DNA immunization or when it was delivered as a subunit protein vaccine formulated either with the MF59 adjuvant or by incorporation into immune-stimulating complexes (ISCOMs) were compared. Virus-neutralizing antibodies (NA) against HIV-1SF2reached similar titers in the two rgp120SF2protein-immunized groups, but the responses showed different kinetics, while NA were delayed and their levels were low in the DNA-immunized animals. Antigen-specific gamma interferon (IFN-γ) T-helper (type 1-like) responses were detected in the DNA-immunized group, but only after the fourth immunization, and the rgp120/MF59 group generated both IFN-γ and interleukin-4 (IL-4) (type 2-like) responses that appeared after the third immunization. In contrast, rgp120/ISCOM-immunized animals rapidly developed marked IL-2, IFN-γ (type 1-like), and IL-4 responses that peaked after the second immunization. To determine which type of immune responses correlated with protection from infection, all animals were challenged intravenously with 50 50% infective doses of a rhesus cell-propagated, in vivo-titrated stock of a chimeric simian immunodeficiency virus-HIVSF13construct. Protection was observed in the two groups receiving the rgp120 subunit vaccines. Half of the animals in the ISCOM group were completely protected from infection. In other subunit vaccinees there was evidence by multiple assays that virus detected at 2 weeks postchallenge was effectively cleared. Early induction of potent type 1- as well as type 2-like T-helper responses induced the most-effective immunity.
Persistent Infection of Human Oligodendrocytic and Neuroglial Cell Lines by Human Coronavirus 229E
Authors: Arbour Nathalie , Ekandé Sophie , Côté Geneviève , Lachance Claude , Chagnon Fanny , Tardieu Marc , Cashman Neil R. , Talbot Pierre J. 
Published: December 2019

ABSTRACT
Human coronaviruses (HuCV) cause common colds. Previous reports suggest that these infectious agents may be neurotropic in humans, as they are for some mammals. With the long-term aim of providing experimental evidence for the neurotropism of HuCV and the establishment of persistent infections in the nervous system, we have evaluated the susceptibility of various human neural cell lines to acute and persistent infection by HuCV-229E. Viral antigen, infectious virus progeny and viral RNA were monitored during both acute and persistent infections. The astrocytoma cell lines U-87 MG, U-373 MG, and GL-15, as well as neuroblastoma SK-N-SH, neuroglioma H4, and oligodendrocytic MO3.13 cell lines, were all susceptible to an acute infection by HuCV-229E. The CHME-5 immortalized fetal microglial cell line was not susceptible to infection by this virus. The MO3.13 and H4 cell lines also sustained a persistent viral infection, as monitored by detection of viral antigen and infectious virus progeny. Sequencing of the S1 gene from viral RNA after ∼130 days of infection showed two point mutations, suggesting amino acid changes during persistent infection of MO3.13 cells but none for H4 cells. Thus, persistent in vitro infection did not generate important changes in the S1 portion of the viral spike protein, which was shown for murine coronaviruses to bear hypervariable domains and to interact with cellular receptor. These results are consistent with the potential persistence of HuCV-229E in cells of the human nervous system, such as oligodendrocytes and possibly neurons, and the virus’s apparent genomic stability.
Mutagenic Analysis of the 3′cis-Acting Elements of the Rubella Virus Genome
Authors: Chen Min-Hsin , Frey Teryl K. 
Published: December 2019

ABSTRACTThermodynamically predicted secondary structure analysis of the 3′-terminal 305 nucleotides (nt) of the rubella virus (RUB) genome, a region conserved in all RUB defective interfering RNAs, revealed four stem-loop (SL) structures; SL1 and SL2 are both located in the E1 coding region, while SL3 and SL4 are within the 59-nt 3′ untranslated region (UTR) preceding the poly(A) tract. SL2 is a structure shown to interact with human calreticulin (CAL), an autoantigen potentially involved in RUB RNA replication and pathogenesis. RNase mapping indicated that SL2 and SL3 are in equilibrium between two conformations, in the second of which the previously proposed CAL binding site in SL2, a U-U bulge, is not formed. Site-directed mutagenesis of the 3′ UTR with a RUB infectious clone, Robo302, revealed that most of the 3′ UTR is required for viral viability except for the 3′-terminal 5 nt and the poly(A) tract, although poly(A) was rapidly regenerated during subsequent replication. Maintenance of the overall SL3 structure, the 11-nt single-stranded sequence between SL3 and SL4, and the sequences forming SL4 were all important for viral viability. Studies on the interaction between host factors and the 3′ UTR showed the formation of three RNA-protein complexes by gel mobility shift assay, and UV-induced cross-linking detected six host protein species, with molecular masses of 120, 80, 66, 55, 48, and 36 kDa, interacting with the 3′ UTR. Site-directed mutagenesis of SL2 by nucleotide substitutions showed that maintenance of SL2 stem rather than the U-U bulge was critical in CAL binding since mutants having the U-U bulge base paired had a similar binding activity for CAL as the native structure whereas mutants having the SL2 stem destabilized had much lower binding activity. However, all of these mutations gave rise to viable viruses when introduced into Robo302, indicating that binding of CAL to SL2 is independent of viral viability.
Activation of Baculovirus Very Late Promoters by Interaction with Very Late Factor 1
Authors: Yang Song , Miller Lois K. 
Published: December 2019

ABSTRACT

Very late factor 1 (VLF-1) of
Autographa californica
multicapsid nuclear polyhedrosis virus (Ac
M
NPV) activates the transcription of two genes, polyhedrin (
polh
) and
p10
, during the final, occlusion-specific phase of infection. Using transient expression assays responsive to VLF-1, we identified linker scan mutations in the
polh
and
p10
promoters which abolished or weakened the ability of the promoters to respond to stimulation by VLF-1. These mutations were located between the transcriptional and translational initiation sites, a region previously shown to be essential for the burst of expression during the very late phase. Addition of partially purified, epitope-tagged VLF-1 to DNA encompassing this “burst sequence” resulted in a shift in the gel electrophoretic mobility of the DNA, indicating that VLF-1 forms a complex with DNA. Addition of an antibody specific for the epitope tag of VLF-1 decreased the mobility of the DNA further, confirming the presence of VLF-1 in the complex. DNase I footprint assays revealed that VLF-1 partially purified from either insect cells or bacterial cells interacted with the burst sequences of both the
polh
and
p10
very-late promoters. Linker scan mutations within the burst sequences severely impaired interaction between VLF-1 and the promoters. We propose that VLF-1 transactivates the
polh
and
p10
promoters by interacting with the burst sequences.
Systemic and Central Nervous System Correction of Lysosomal Storage in Mucopolysaccharidosis Type VII Mice
Authors: Stein Colleen S. , Ghodsi Abdi , Derksen Todd , Davidson Beverly L. 
Published: December 2019

ABSTRACT
Mucopolysaccharidosis (MPS) type VII patients lack functional β-glucuronidase, leading to systemic and central nervous system dysfunction. In this study we tested whether recombinant adenovirus that encodes β-glucuronidase (Adβgluc), delivered intravenously and into the brain parenchyma of MPS type VII mice, could provide long-term transgene expression and correction of lysosomal distension. We also tested whether systemic treatment with the immunosuppressive anti-CD40 ligand antibody, MR-1, affected transgene expression. We found substantial plasma β-glucuronidase activity for over 9 weeks after gene transfer in the MR-1- treated group, with subsequent decline in activity corresponding to a delayed anti-β-glucuronidase antibody response. At 16 weeks, near wild-type amounts of β-glucuronidase activity and striking reduction of lysosomal pathology were detected in livers from mice that had received either MR-1 cotreatment or control antibody. In the lung and kidney, β-glucuronidase activity was markedly higher for the MR-1-treated group. β-Glucuronidase activity in the brain persisted independently of MR-1 treatment. Activity was intense in the injected hemisphere and was also evident in the noninjected cortex and striatum, with dramatic improvements in storage deposits in areas of both hemispheres. These results indicate that prolonged enzyme expression from transgenes delivered to deficient liver and brain can mediate pervasive correction and illustrate the potential for gene therapy of MPS and other lysosomal storage diseases.
Effects of Human Immunodeficiency Virus Type 1 Resistance to Protease Inhibitors on Reverse Transcriptase Processing, Activity, and Drug Sensitivity
Authors: de la Carrière Laurence Carron , Paulous Sylvie , Clavel François , Mammano Fabrizio 
Published: December 2019

ABSTRACT
Human immunodeficiency virus type 1 (HIV-1) variants resistant to protease inhibitors often display a reduced replicative capacity as a result of an impairment of protease function. Such fitness-impaired viruses display Gag precursor maturation defects. Here, we report that some protease inhibitor-resistant viruses also display abnormalities in the processing of reverse transcriptase (RT) by the protease. In three recombinant viruses carrying resistant protease sequences from patient plasma, we observed a marked decrease in the amount of mature RT subunits and of particle-associated RT activity compared to their parental pretherapy counterparts. We investigated the possibility that a decrease in the amount of particle-associated mature RT could affect the sensitivity of the corresponding virus to RT inhibitors. We observed a twofold increase of sensitivity to zidovudine (AZT) when a virus which carried AZT mutations was processed by a resistant protease. Interestingly, the presence of AZT-resistance mutations partially rescued the replication defect associated with the mutated protease. The interplay between resistance to protease inhibitors and to RT inhibitors described here may be relevant to the therapeutic control of HIV-1 infection.