Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “lytic replication”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2006

Unexpected structure of Epstein-Barr virus lytic cycle activator Zta.

The key viral gene responsible for initiating the replicative cycle of Epstein-Barr virus (EBV), termed BZLF1, encodes the multifunctional protein Zta (ZEBRA or Z). It interacts with DNA as both a transcription and a replication factor, modulates both intracellular signal transduction and the DNA-damage response and manipulates cell cycle progression. Muller and colleagues have resolved the structure of Zta bound to DNA, which confirms some structural predictions but reveals an unexpected twist and a complex dimerization interface. Because EBV is associated with human disease, Zta presents a prime target for drug design.

Amino Acid Sequence↗
PubMed1978

Construction of a hybrid bacteriophage-plasmid recombinant DNA vector.

A phage-plasmid hybrid was constructed for use as a recombinant DNA vector, allowing the propagation of cloned EcoRI restriction endonuclease fragments of about 2 X 10(6) to 11 X 10(6) daltons. The colicin E1 plasmid replicon was fused to the left arm of a lambdagt generalized transducing phage with a thermolabile repressor, yielding a genome which could be replicated either by phage lambda functions or via the colicin E1 plasmid replicon. At the nonpermissive temperature, phage functions were derepressed and phage growth occurred lytically. Alternatively, at the permissive temperature, lambda functions were repressed and the vector replicated as a covalently closed circular plasmid. The phage-plasmid hybrid vector could be maintained at a copy number determined by the colicin E1 plasmid replicon and was also sensitive to amplification after chloramphenicol treatment. An EcoRI fragment of Escherichia coli DNA encoding genes of the arabinose operon also was inserted into the central portion of the vector.

Chloramphenicol↗
PubMed2002

Human cytomegalovirus UL84 localizes to the cell nucleus via a nuclear localization signal and is a component of viral replication compartments.

The UL84 open reading frame encodes a protein that is required for origin-dependent DNA replication and interacts with the immediate-early protein IE2 in lytically infected cells. Transfection of UL84 expression constructs showed that UL84 localized to the nucleus of transfected cells in the absence of any other viral proteins and displayed a punctate speckled fluorescent staining pattern. Cotransfection of all the human cytomegalovirus replication proteins and oriLyt, along with pUL84-EGFP, showed that UL84 colocalized with UL44 (polymerase accessory protein) in replication compartments. Experiments using infected human fibroblasts demonstrated that UL84 also colocalized with UL44 and IE2 in viral replication compartments in infected cells. A nuclear localization signal was identified using plasmid constructs expressing truncation mutants of the UL84 protein in transient transfection assays. Transfection assays showed that UL84 failed to localize to the nucleus when 200 amino acids of the N terminus were deleted. Inspection of the UL84 amino acid sequence revealed a consensus putative nuclear localization signal between amino acids 160 and 171 (PEKKKEKQEKK) of the UL84 protein.

Animals↗
PubMedDate not supplied

Investigation of bacteriophage MS2 viral dynamics using model discrimination analysis and the implications for phage therapy.

Lytic phages infect their bacterial hosts, use the host machinery to replicate, and finally lyse and kill their hosts, releasing progeny phages. Various mathematical models have been developed that describe these phage-host viral dynamics. The aim of this study was to determine which of these models best describes the viral dynamics of lytic RNA phage MS2 and its host Escherichia coli C-3000. Experimental data consisted of uninfected and infected bacterial cell densities, free phage density, and substrate concentration. Parameters of various models were either determined directly through other experimental techniques or estimated using regression analysis of the experimental data. The models were evaluated using a Bayesian-based model discrimination technique. Through model discrimination it was shown that phage-resistant cells inhibited the growth of phage population. It was also shown that the uninfected bacterial population was a quasispecies consisting of phage-sensitive and phage-resistant bacterial cells. When there was a phage attack the phage-sensitive cells died out and the phage-resistant cells were selected for and became the dominant strain of the bacterial population.

Cell Proliferation↗
PubMed1982

Mapping the in vivo arrangement of nucleosomes on simian virus 40 chromatin by the photoaddition of radioactive hydroxymethyltrimethylpsoralen.

Intracellular simian virus 40 (SV40) chromatin was photoreacted with a 3H-labeled psoralen derivative, hydroxymethyltrimethylpsoralen (HMT), at 48 h postinfection. Psoralen compounds have been shown to readily penetrate intact cells and, in the presence of long-wavelength UV light, form covalent adducts to DNA, preferentially at regions unprotected by nucleosomes. The average distribution pattern of [3H]HMT on the SV40 genome was determined by specific activity measurements of the DNA fragments generated by HindIII plus HpaII or by AtuI restriction enzyme digestion. At levels of 1 to 10 [3H]HMT photoadducts per SV40 molecule, the radiolabel was found to be distributed nonrandomly. Comparison of the labeling pattern in vivo with that of purified SV40 DNA labeled in vitro revealed one major difference. A region of approximately 400 base pairs, located between 0.65 and 0.73 on the physical map, was preferentially labeled under in vivo conditions. This finding strongly suggests that the highly accessible region near the origin of replication, previously observed on isolated SV40 "minichromosomes," exists on SV40 chromatin in vivo during a lytic infection.

Binding Sites↗
PubMedDate not supplied

Coxsackievirus B3-induced chronic myocarditis in outbred NMRI mice.

OBJECTIVES: The pathogenesis of coxsackievirus B3 (CVB3)-induced myocarditis was investigated in adult Han:NMRI mice. The outbred model, in comparison with inbred models, represents better the natural variable susceptibility of the human population. STUDY DESIGN/METHODS: We analyzed the replicating virus titer, the antibody response in the acute and chronic phase of disease, the histology of myocardial injury, and the persistence of viral RNA. RESULTS: NMRI mice infected with 5000 plaque-forming units (PFU) of the CVB3 variant "P"D, a lytic variant to human fibroblast lines, showed a peak of virus replication at day 14 and developed a severe acute myocarditis. The chronic myocarditis was characterized by progressive fibrosis, small foci of infiltrates, persistent viral RNA in the heart, and detectable anti-CVB3 IgG production and neutralizing antibody response up to day 98 postinfection. CONCLUSIONS: CVB3"P"D is able to induce chronic myocarditis in NMRI mice. This model provides a method for examining and proving the mechanisms of myocardial pathogenesis and of developing therapeutic strategies.

Animals↗
PubMed1989

Replication-dependent activation of the adenovirus major late promoter is mediated by the increased binding of a transcription factor to sequences in the first intron.

During lytic infection, the adenovirus major late promoter (MLP) is primarily activated after the onset of viral DNA replication. Using a combination of DNA binding and in vitro transcription assays, we delineated a discrete MLP element spanning positions +80 to +106 which is essential for the replication-dependent activation of this promoter. We also identified a 40-kilodalton protein (the downstream element factor [DEF]) which binds to the +86-TTGTCAGTTT-+95 motif within this element. Whereas the DEF-binding activity is barely detectable in uninfected cells, it is readily visualized in adenovirus-infected cells, but only after the onset of viral DNA replication. Preventing the interaction of DEF with the MLP template impairs the in vitro transcriptional stimulation. We conclude that this replication-dependent activation of the MLP is, at least in part, mediated by induction of the specific binding of DEF to the MLP downstream element.

Adenoviruses, Human↗
PubMed1995

Biological and genetic changes in ovine lentivirus strains following passage in isogeneic twin lambs.

Ovine lentivirus (OvLV) strains vary in cytopathogenicity, but the correlation, if any, between viral cytophenotypes and in vivo pathogenicity is poorly understood. To examine this issue and to evaluate changes in OvLV strains following passage in vivo, biological and genetic characteristics of OvLV isolates following in vivo passage were compared with those of the parent strain used for inoculation of two sets of isogeneic twin lambs. Plaque-purified OvLV strains with "slow/low" (84/28) and "rapid/high" (85/34) cell culture phenotypes were used for inoculation of the lambs. The phenotypes of the parent OvLV strains were compared with virus isolates from the four lambs by assaying virus replication and cytopathogenicity in goat synovial membrane cells. Viral population genetic differences in the env region were compared by polymerase chain reaction (PCR) amplification and denaturing gradient gel electrophoresis (DGGE) of the fragments. Virus isolates recovered from rapid/high virus-infected sheep were more lytic and developed syncytia earlier than viruses reisolated from sheep inoculated with the slow/low strain. Isolates from lambs infected with 84/28 were more cytopathic in all assays than was their parent strain. Isolates from animals infected with 85/34 were more lytic and syncytiogenic than the parent strain, but responded similarly in replication assays. Although there were no consistent phenotypic differences between virus isolates recovered from sets of twins with markedly different degrees of lymphoid interstitial pneumonia (LIP), the DGGE band patterns of PCR amplified env fragments of the virus isolates from the twin lamb set with severe LIP, but not the set with slight LIP, were distinctly different from those of the parental viruses.

Animals↗
PubMed1994

Inhibition of HIV replication by CD8+ T cells correlates with CD4 counts and clinical stage of disease.

We sought to evaluate the relationship of CD8+ T cell-mediated inhibition of autologous HIV replication in vitro to disease stage in HIV+ individuals. Depletion of CD8+ T cells from peripheral blood lymphocytes of 16 HIV+ subjects increased the percentage of virus-producing cultures from 56% to 81%. CD4+ T cells were purified from 52 HIV+ individuals and cultured alone or in the presence of autologous CD8+ T cells. In 13 (25%) subjects HIV replication was only detected in the absence of CD8+ T cells (inhibition positive); in 26 (50%) viral replication occurred both in the absence and presence of CD8+ cells (inhibition negative). In the remaining 13 (25%) subjects, CD8+ T cell-mediated inhibitory activity could not be evaluated because stimulation of their purified CD4+ T cells did not result in p24 production. In some virus culture-negative individuals, the inability to demonstrate HIV replication was due to the presence of low numbers of CD8+ T cells that co-purified with CD4+ T cells. Detection of inhibitory CD8+ T cells was associated with significantly higher CD4 counts and better clinical status compared with inhibition-negative subjects. These results demonstrate that CD8+ T cell-mediated inhibition of HIV replication correlates with disease stage, and thus may play a role in preventing disease progression. CD8+ T cells did not inhibit autologous HIV replication across a semipermeable membrane. Further, the ability of CD8+ T cells to prevent HIV replication did not correlate with lysis of autologous CD4+ T cells. Thus, CD8+ T cells inhibited autologous HIV replication in vitro through a contact-mediated non-lytic mechanism.

CD4-Positive T-Lymphocytes↗
PubMed2003

[Transposition as a way of existence: phage Mu].

Transposition is a special mode of DNA recombination that produces a transfer of a DNA segment (transposable element, TE) from one chromosome region to a nonhomologous genomic loci. Bacterial TEs have chosen two principal strategies of their movement within and among genomes: conservative transposition (resulting in a simple insertion) and/or replicative transposition (accompanied by complete DNA replication and producing a cointegrate). Variations of transposition strategies concern the number and nature of cuts that sever the transposon from the flanking donor DNA: one-strand break (phage Mu) or double-strand breaks (Tn7, IS10 and members of IS3 family) and the possibility of accompanying TE replication, which leads to different end-products of transposition. Phage Mu combines properties of a temperate phage and a transposable element. Among transposons, it is studied in most detail. As a transposable element phage Mu is remarkable because its life-cycle involves two transposition modes: non-replicative resulting in lysogeny and replicative leading to multiple copying of phage DNA during the lytic growth. There are several levels of transcription regulation (or choice of developmental pathway). The genetic transposition reaction mediated by phage Mu A transposase A in the transpososome complex involves elaborate protein-nucleic acid and protein-protein interactions.

Animals↗
PubMed1999

Induction of lytic Epstein-Barr virus (EBV) infection in EBV-associated malignancies using adenovirus vectors in vitro and in vivo.

The consistent presence of EBV genomes in certain tumor types (in particular, AIDS-related central nervous system lymphomas and nasopharyngeal carcinomas) may allow novel, EBV-based targeting strategies. Tumors contain the latent (transforming) form of EBV infection. However, expression of either of the EBV immediate-early proteins, BZLF1 and BRLF1, is sufficient to induce lytic EBV infection, resulting in death of the host cell. We have constructed replication-deficient adenovirus vectors expressing the BZLF1 or BRLF1 immediate-early genes and examined their utility for killing latently infected lymphoma cells in vitro and in vivo. We show that both the BZLF1 and BRLF1 vectors efficiently induce lytic EBV infection in Jijoye cells (an EBV-positive Burkitt lymphoma cell line). Furthermore, lytic EBV infection converts the antiviral drug, ganciclovir (GCV), into a toxic (phosphorylated) form, which inhibits cellular as well as viral DNA polymerase. When Jijoye cells are infected with the BZLF1 or BRLF1 adenovirus vectors in the presence of GCV, viral reactivation is induced, but virus replication is inhibited (thus preventing the release of infectious EBV particles); yet cells are still efficiently killed. Finally, we demonstrate that the BZLF1 and BRLF1 adenovirus vectors induce lytic EBV infection when they are directly inoculated into Jijoye cell tumors grown in severe combined immunodeficiency mice. These results suggest that induction of lytic EBV infection in tumors, in combination with GCV, may be an effective strategy for treating EBV-associated malignancies.

Adenoviridae↗
PubMed1996

Antisense oligodeoxynucleotides against the BZLF1 transcript inhibit induction of productive Epstein-Barr virus replication.

Expression of the Epstein-Barr virus (EBV) BZLF1 gene product, ZEBRA, in latently infected cells is sufficient to induce the viral lytic cycle. The use of oligodeoxynucleotides complementary to the BZLF1 transcript was studied to inhibit this induction of productive viral replication. For this purpose, we employed oligodeoxynucleotides complementary to the translation initiation codons and their flanking sequences. Incubation of Akata cells with the 25-mer phosphodiester (PO)- or phosphorothioate (PS)-antisense oligodeoxynucleotides for 3 h before stimulation with anti-immunoglobulin G antibodies (anti-IgG) partially inhibited the anti-IgG-mediated induction of ZEBRA synthesis. Both the PO- and PS-antisense oligodeoxynucleotide treatments also suppressed the productive EBV replication (as measured by linear DNA production) in a dose-dependent manner, with much greater efficiency than did PO and PS-oligodeoxynucleotides with sense, reverse or random sequences of the same length. Another 20-mer antisense oligodeoxynucleotide complementary to sequences downstream of the translation initiation codons showed a similar inhibitory effect on EBV replication. However, the inhibition was considerably lower when the cells were treated with oligodeoxynucleotides complementary to sequences upstream of the start codons. These results indicate that BZLF1 antisense oligodeoxynucleotides inhibit the viral activation in a sequence-specific fashion. In the virus-producer cell line P3HR-1, the same PS-antisense oligodeoxynucleotides also partially suppressed the spontaneous viral replication after 6-10 days, substantially more than the PS-random oligodeoxynucleotides. Inhibition of BZLF1 appears to be sufficient to suppress the induction of EBV replication.

Antigens, Viral↗
PubMed2004

Generation of a latency-deficient gammaherpesvirus that is protective against secondary infection.

Kaposi's sarcoma-associated herpesvirus and murine gammaherpesvirus-68 (MHV-68) establish latent infections and are associated with various types of malignancies. They are members of the gamma-2 herpesvirus subfamily and encode a replication and transcriptional activator, RTA, which is necessary and sufficient to disrupt latency and initiate the viral lytic cycle in vitro. We have constructed a recombinant MHV-68 virus that overexpresses RTA. This virus has faster replication kinetics in vitro and in vivo, is deficient in establishing latency, exhibits a reduction in the development of a mononucleosis-like disease in mice, and can protect mice against challenge by wild-type MHV-68. The present study, by using MHV-68 as an in vivo model system, demonstrated that RTA plays a critical role in the control of viral latency and suggests that latency is a determinant of viral pathogenesis in vivo.

Animals↗
PubMed1994

Neighboring plasmid sequences can affect Mini-Mu DNA transposition in the absence of expression of the bacteriophage Mu semi-essential early region.

Bacteriophage Mu DNA, like other transposable elements, requires DNA sequences at both extremities to transpose. It has been previously demonstrated that the transposition activity of various transposons can be influenced by sequences outside their ends. We have found that alterations in the neighboring plasmid sequences near the right extremity of a Mini-Mu, inserted in the plasmid pSC101, can exert an influence on the efficiency of Mini-Mu DNA transposition when an induced helper Mu prophage contains a polar insertion in its semi-essential early region (SEER). The SEER of Mu is known to contain several genes that can affect DNA transposition, and our results suggest that some function(s), located in the SEER of Mu, may be required for optimizing transposition (and thus, replication) of Mu genomes from restrictive locations during the lytic cycle.

Bacteriophage mu↗
PubMedDate not supplied

Enzyme-linked immunosorbent assay for antibodies to ZEBRA, an Epstein-Barr trans-activator.

Patients with AIDS and AIDS-related complex often show symptoms of Epstein-Barr virus (EBV) reactivation. Several EBV-encoded trans-acting factors activate the EBV lytic cycle, and one, called ZEBRA (BamHI Z EBV replication activator), controls the switch of EBV from a latent to a productive cycle. We describe here a simple ELISA test using a bacterially expressed ZEBRA protein as antigen. Utilizing this technique, we evaluated the humoral response to ZEBRA antigen in 38 patients with nasopharyngeal carcinoma and 134 subjects with an asymptomatic HIV 1 infection. The control group consisted of 40 healthy adult blood donors.

Antibodies, Viral↗
PubMed2004

Herpes simplex virus infections are arrested in Oct-1-deficient cells.

Expression of the herpes simplex virus (HSV) immediate early (IE) genes is regulated by a multiprotein complex that is assembled on the TAATGARAT enhancer core element. The complex contains the cellular POU domain protein Oct-1, the viral transactivator VP16, and the cellular cofactor host cell factor 1. The current model suggests that the assembly depends on recognition of the core element by Oct-1. Here, HSV infection of Oct-1-deficient mouse embryonic fibroblast cells demonstrates that Oct-1 is critical for IE gene expression at low multiplicities of infection (moi). However, the protein is not essential for IE gene expression at high moi, indicating that VP16-mediated transcriptional induction through other IE regulatory elements is also important. This induction depends, at least in part, on the GA-binding protein binding elements that are present in each IE enhancer domain. Surprisingly, whereas the viral IE genes are expressed after high moi infection of Oct-1-deficient cells, the assembly of viral replication factories is severely impaired, revealing a second critical role for Oct-1 in HSV replication. The results have implications for both the HSV lytic and latency-reactivation cycles.

3T3 Cells↗
PubMed1992

Adenovirus E1A, simian virus 40 tumor antigen, and human papillomavirus E7 protein share the capacity to disrupt the interaction between transcription factor E2F and the retinoblastoma gene product.

The adenovirus E1A gene product, the simian virus 40 large tumor antigen, and the human papillomavirus E7 protein share a short amino acid sequence that constitutes a domain required for the transforming activity of these proteins. These sequences are also required for these proteins to bind to the retinoblastoma gene product (pRb). Recent experiments have shown that E1A can dissociate complexes containing the transcription factor E2F bound to pRb, dependent on this conserved sequence element. We now show that the E7 protein and the simian virus 40 large tumor antigen can dissociate the E2F-pRb complex, dependent on this conserved sequence element. We also find that the E2F-pRb complex is absent in various human cervical carcinoma cell lines that either express the E7 protein or harbor an RB1 mutation, suggesting that the loss of the E2F-pRb interaction may be an important aspect in human cervical carcinogenesis. We suggest that the ability of E1A, the simian virus 40 large tumor antigen, and E7 to dissociate the E2F-pRb complex may be a common activity of these viral proteins that has evolved to stimulate quiescent cells into a proliferating state so that viral replication can proceed efficiently. In circumstances in which a lytic infection does not proceed, the consequence of this action may be to initiate the oncogenic process in a manner analogous to the mutation of the RB1 gene.

Adenovirus Early Proteins↗
PubMed1986

Characterization of the restricted component of Epstein-Barr virus early antigens as a cytoplasmic filamentous protein.

Four monoclonal antibodies produced against the restricted component of the Epstein-Barr virus (EBV) early antigen (EA-R) precipitated a polypeptide with an approximate molecular weight of 85,000. Three of these antibodies prepared against the native 85,000-molecular-weight protein (85K protein) reacted by immunofluorescence with acetone-fixed smears but not methanol-fixed smears of EBV-producing cells activated with tumor-promoting agent and sodium butyrate. The fourth monoclonal antibody which was produced against the denatured 85K protein reacted with both acetone-fixed cells and methanol-fixed cells. Blocking of direct immunofluorescence by the different monoclonal antibodies established that these monoclonal antibodies were directed against three different epitopes expressed on the 85K protein. The cytoplasmic staining pattern produced by each antibody was granular during the first 24 to 28 h after induction, developed into filamentous structures about 36 h after induction, and then began to aggregate after 48 h. Similar structures were observed in human placental cells transfected by EBV DNA and stained with three of the monoclonal antibodies. These results suggest that the EA-R polypeptide is assembled into filaments during the EBV lytic cycle. The significance of this in regards to replication has yet to be determined. Biochemical characterization of this major EA-R component did not reveal any major differences in this protein isolated from different cell lines.

Amino Acids↗