Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genes, Viral”

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 19 recordsLinked to original sources
PubMed1990

Binding sites in mammalian genes and viral gene regulatory regions recognized by methylated DNA-binding protein.

Methylated DNA-binding protein (MDBP), a ubiquitous mammalian protein, recognizes a variety of related DNA sequences. Some of these sequences require methylation of their CpG dinucleotides for binding and others do not. We report that MDBP binds, in a DNA methylation-independent fashion, to two sites in the mouse polyomavirus enhancer, one in the enhancer of the human hepatitis B virus, and to one in the long terminal repeat of equine infectious anemia proviral DNA. We have also found a number of MDBP sites in human and rodent DNAs which bind much better to MDBP when they are methylated at CpG dinucleotides within the recognition site. These include sites at the beginning of the human genes for hypoxanthine phosphoribosyl transferase, HLA-A2, -A3, and -A25 antigens, and alpha-galactosidase A. In the case of methylation-responsive MDBP sites, changes in their methylation status during differentiation or DNA replication could help drive development by modulating transcription.

Animals↗
PubMed2003

Molecular anatomy of Tupaia (tree shrew) adenovirus genome; evolution of viral genes and viral phylogeny.

Adenoviruses are globally spread and infect species in all five taxons of vertebrates. Outstanding attention is focused on adenoviruses because of their transformation potential, their possible usability as vectors in gene therapy and their applicability in studies dealing with, e.g. cell cycle control, DNA replication, transcription, splicing, virus-host interactions, apoptosis, and viral evolution. The accumulation of genetic data provides the basis for the increase of our knowledge about adenoviruses. The Tupaia adenovirus (TAV) infects members of the genus Tupaiidae that are frequently used as laboratory animals in behavior research dealing with questions about biological and molecular processes of stress in mammals, in neurobiological and physiological studies, and as model organisms for human hepatitis B and C virus infections. In the present study the TAV genome underwent an extensive analysis including determination of codon usage, CG depletion, gene content, gene arrangement, potential splice sites, and phylogeny. The TAV genome has a length of 33,501 bp with a G+C content of 49.96%. The genome termini show a strong CG depletion that could be due to methylation of these genome regions during the viral replication cycle. The analysis of the coding capacity of the complete TAV genome resulted in the identification of 109 open reading frames (ORFs), of which 38 were predicted to be real viral genes. TAV was classified within the genus Mastadenovirus characterized by typical gene content, arrangement, and homology values of 29 conserved ORFs. Phylogenetic trees show that TAV is part of a separate evolutionary lineage and no mastadenovirus species can be considered as the most related. In contrast to other mastadenoviruses a direct ancestor of TAV captured a DUT gene from its mammalian host, presumably controlling local dUTP levels during replication and enhance viral replication in non-dividing host tissues. Furthermore, TAV possesses a second DNA-binding protein gene, that is likely to play a role in the determination of the host range. In view of these data it is conceivable that TAV underwent evolutionary adaptations to its biological environment resulting in the formation of special genomic components that provided TAV with the ability to expand its host range during viral evolution.

Adenoviridae Infections↗
PubMed1986

A genetic approach to promoter recognition during trans induction of viral gene expression.

Viral infection of mammalian cells entails the regulated induction of viral gene expression. The induction of many viral genes, including the herpes simplex virus gene encoding thymidine kinase (tk), depends on viral regulatory proteins that act in trans. Because recognition of the tk promoter by cellular transcription factors is well understood, its trans induction by viral regulatory proteins may serve as a useful model for the regulation of eukaryotic gene expression. A comprehensive set of mutations was therefore introduced into the chromosome of herpes simplex virus at the tk promoter to directly analyze the effects of promoter mutations on tk transcription. The promoter domains required for efficient tk expression under conditions of trans induction corresponded to those important for recognition by cellular transcription factors. Thus, trans induction of tk expression may be catalyzed initially by the interaction of viral regulatory proteins with cellular transcription factors.

Animals↗
PubMed2005

Valproic acid enhances gene expression from viral gene transfer vectors.

Viral vectors represent an efficient delivery method for in vitro and in vivo gene transfer, and their utility may be further enhanced through the use of pharmacologic agents that increase gene expression. Here, we demonstrate that valproic acid (VPA), a drug which is widely used for the treatment of epilepsy and mood disorders, enhances and prolongs expression of exogenous genes in cells transduced with various gene transfer agents, including adenovirus, adeno-associated virus and herpesvirus vectors. This effect occurs in a wide range of cell types, including both primary cells and cell lines, and appears to be associated with VPA's ability to function as a histone deacetylase inhibitor (HDACi). VPA treatment also enhanced adenovirally-vectored expression of a luciferase reporter gene in mice, as demonstrated by in vivo imaging. VPA was also less cytotoxic than a commonly used HDAC inhibitor, TSA, suggesting its use as a safer alternative. Taken together, these results suggest that VPA treatment may represent a useful approach to various gene transfer approaches in which enhanced transgene expression is desirable.

Adenoviridae↗
PubMed1978

Endogenous viral genes of the White Leghorn chicken: common site of residence and sites associated with specific phenotypes of viral gene expression.

The DNAs from greater than 150 individual White Leghorn chickens were digested with restriction endonucleases BamHI, EcoRI, HindIII, and Sst I, fractionated by gel electrophoresis, denatured, and transferred to nitrocellulose filters. Fragments containing the endogenous viral genes were detected by hybridization with 70S Rous associated virus type 2[32P]RNA. Embryos of several different phenotypes with respect to production of the endogenous virus and expression of viral group-specific antigen and viral envelope protein were analyzed. DNA from birds of each phenotype produced a distinctive pattern of fragments containing viral genetic information. Individual fragments were seen to segregate as genetic loci in mating experiments. From the fragment patterns and the segregation data, the following conclusions were drawn with respect to the sites of residence in the chicken chromosome of the endogenous viral genes: (i) the DNA of all chickens contains viral genetic information in at least one site, and this site of residence appears to be the same in all chickens analyzed; (ii) four other sites have been identified, and the presence of viral information at each of these sites is always accompanied by a specific phenotype of endogenous viral gene expression; (iii) in addition to the above-mentioned five sites, a small number of other sites have been identified which are not associated with a known phenotype.

Animals↗
PubMed1988

A safe packaging line for gene transfer: separating viral genes on two different plasmids.

A retrovirus packaging cell line was constructed by using portions of the Moloney murine leukemia virus in which the gag, pol, and env genes of the helper virus were separated onto two different plasmids and in which the psi packaging signal and 3' long terminal repeat were removed. The plasmid containing the gag and pol genes and the plasmid containing the env gene were cotransfected into NIH 3T3 cells. Clones that produced high levels of reverse transcriptase and env protein were tested for their ability to package the replication-defective retrovirus vectors delta neo and N2. One of the gag-pol and env clones (GP+E-86) was able to transfer G418 resistance to recipient cells at a titer of as high as 1.7 X 10(5) when it was used to package delta neo and as high as 4 X 10(6) when it was used to package N2. Supernatants of clones transfected with the intact parent gag-pol-env plasmid 3P0 had comparable titers (as high as 6.5 X 10(4) with delta neo; as high as 1.7 X 10(5) with N2). Tests for recombination events that might result in intact retrovirus showed no evidence for the generation of replication-competent virus. These results suggest that gag, pol, and env, when present on different plasmids, may provide an efficient and safe packaging line for use in retroviral gene transfer.

Animals↗
PubMed1994

Non-viral gene therapy.

Non-viral gene therapies are currently under development that employ drug-delivery methods for targeting genes to selected cells in the body, where they express therapeutic gene products. Various methods have been described for non-viral gene therapy, ranging from the direct intramuscular injection of purified DNA to the systemic administration of formulations comprising DNA and lipids, proteins, peptides, or polymers. Products for non-viral gene therapies are designed both for direct administration to patients by conventional routes and for expression of a therapeutic product over a finite period of time in a manner similar to conventional medicines. Initial preclinical and clinical studies indicate that non-viral gene delivery methods exhibit safety profiles similar to conventional pharmaceutical or biological products. Clinical trials have been proposed, or are currently under way, to assess the applicability of non-viral gene therapy for a variety of disorders, including cystic fibrosis, cancer, and peripheral vascular disease. Non-viral techniques may soon allow gene therapy to be applied in clinical practice alongside conventional medicines for the treatment of common diseases.

Animals↗
PubMed1998

Relationships between polydnavirus genomes and viral gene expression.

Polydnavirus genomes and viral gene functions are atypical for viruses. Polydnaviruses are the only group of viruses with segmented DNA genomes and have an unusual obligate mutualistic association with parasitic Hymenoptera, in which the virus is required for survival of the wasp host and vice versa. The virus replicates asymptomatically in the wasp host but severely disrupts lepidopteran host physiology in the absence of viral DNA replication. It is not surprising then that viral gene expression is divergent in its two insect hosts and that differences in viral gene expression are linked to these divergent functions. Some viral genes are expressed only in the wasp host while other viral genes are expressed only in the lepidopteran host and are presumed to be involved in the disruption of host physiological systems. Our laboratory has described the expression and regulation of a family of viral genes implicated in suppressing the lepidopteran immune system, the cys-motif genes. In conjunction with these studies we have described the physical organization of additional viral gene segments. We have cloned, mapped and begun the sequence analysis of selected viral DNA segments. We have noted that some viral DNA segments are nested and that nested viral DNA segments encode the abundantly expressed, secreted cys-motif genes. Conversely, other viral segments are not nested, encode less abundantly expressed genes and may be targeted intra-cellularly. These results suggest that nesting of segments in polydnavirus genomes may be linked to the levels of gene expression. By extension, the unique, segmented organization of polydnavirus genomes may be associated, in part, with the requirement for divergent levels of viral gene expression in lepidopteran hosts in the absence of viral DNA replication.

Journal Article↗
PubMed1975

Evolution of type C viral genes: preservation of ancestral murine type C viral sequences in pig cellular DNA.

Domestic pigs (Sus scrofa) and other members of the family Suidae have multiple copies of type C viral gene sequences in the cellular DNA of all their tissues. Partially homologous viral gene sequences are also found in cellular DNA of rodents, particularly Muridae. The results lead to the conclusion that type C viral genes were introduced into the Suidae lineage as a result of trans-species infection by an ancestral xenotropic murine virus. The rate of evolution of the virogene sequences in the pig appears to be much slower than that of genes that have remained in the rodent lineage; this may be a consequence of transfer from a shorter-lived animal (the rodent) to a longer-lived one (the pig). We estimate the time of gene transmission as 5-10 million years ago and conclude that the present-day porcine type C virogenes most closely approximate the viral genes as they were several million years ago in the rodent lineage.

Animals↗
PubMed1982

Chicken ovalbumin gene fused to a herpes simplex virus alpha promoter and linked to a thymidine kinase gene is regulated like a viral gene.

We are describing a system for the introduction, selection, and expression of eucaryotic genes in higher eucaryotic cells. The carrier consisted of the herpes simplex virus 1 (HSV-1) tk gene covalently linked to an HSV-1 alpha promoter directed away from the tk gene. In this study we fused to the alpha promoter the 5' transcribed noncoding sequences and the coding sequences of the chicken oviduct ovalbumin gene. Cells converted to the TK+ phenotype with this chimeric fragment produced an ovalbumin precursor which was processed and secreted into the extracellular fluid. The ovalbumin gene utilized the HSV-1 alpha promoter and was regulated as a viral gene inasmuch as inversion of the genomic DNA relative to the alpha promoter resulted in no ovalbumin synthesis, and production of ovalbumin was enhanced after superinfection with HSV-1. Synthesis of ovalbumin was not detected when cDNA was linked to the HSV-1 alpha promoter. The carrier system described in this study is suitable for introduction, selection, and expression of eucaryotic genes whose natural promoter is either weak or requires the presence of regulatory elements which may be absent from undifferentiated cells in culture.

Animals↗
PubMed1995

Human immunodeficiency virus type 1 integrase: effects of mutations on viral ability to integrate, direct viral gene expression from unintegrated viral DNA templates, and sustain viral propagation in primary cells.

Integrase is the only viral protein necessary for integration of retroviral DNA into chromosomal DNA of the host cell. Biochemical analysis of human immunodeficiency virus type 1 (HIV-1) integrase with purified protein and synthetic DNA substrates has revealed extensive information regarding the mechanism of action of the enzyme, as well as identification of critical residues and functional domains. Since in vitro reactions are carried out in the absence of other viral proteins and they analyze strand transfer of only one end of the donor substrate, they do not define completely the process of integration as it occurs during the course of viral infection. In an effort to further understand the role of integrase during viral infection, we initially constructed a panel of 24 HIV-1 mutants with specific alanine substitutions throughout the integrase coding region and analyzed them in a human T-cell line infection. Of these mutant viruses, 12 were capable of sustained viral replication, 11 were replication defective, and 1 was temperature sensitive for viral growth. The replication defective viruses express and correctly process the integrase and Gag proteins. Using this panel of mutants and an additional set of 18 mutant viruses, we identified nine amino acids which, when replaced with alanine, destroy integrase activity. Although none of the replication-defective mutants are able to integrate into the host genome, a subset of them with alterations in the catalytic triad are capable of Tat-mediated transactivation of an indicator gene linked to the viral long terminal repeat promoter. We present evidence that integration of the HIV-1 provirus is essential not only for productive infection of T cells but also for virus passage in both cultured peripheral blood lymphocytes and macrophage cells.

Base Sequence↗
PubMed2003

Viral genes and methylation.

Epigenetics represents a new frontier in cancer research. Methylation is the best studied of the epigenetic mechanisms that regulate gene expression. Regulation of gene expression by means of methylation has been reported for tumor suppressor genes, oncogenes, viral promoters, and age-related genes. In this review, the regulation of viral gene expression by methylation is discussed, with particular emphasis on: (1) the virus-specific factors that bind to promoter regions; (2) the implications of this knowledge for designing viral vectors that can be used to deliver genes for the purpose of gene therapy; and (3) the use of this knowledge for the early detection and prevention of cancer. Since methylation can be reversed by a variety of exogenous agents, great potential exists to develop interventions that target cancer-associated aberrant methylation in an effort to reverse or prevent carcinogenesis.

Animals↗
PubMed1999

Viral gene delivery.

Experimental studies of viral gene delivery generally support the principle that virus-mediated gene transfer is indeed possible. However, the field of gene therapy has not yet been realised as a practicable clinical intervention. The delay in translation of laboratory work to clinical utility largely reflects the inability of gene delivery vectors to convey adequate genetic material to a desired location, with adequate durability and low enough toxicity to be effective. Current studies of viral gene therapy vehicles have focused on re-engineering viruses being tested as vectors at present, treating the host to facilitate viral gene transfer and the development of new vectors. Initial enthusiasm for oncoretroviral and adenoviral vectors has cooled, while adeno-associated virus and lentiviral vectors are attracting more interest. Experimental studies with modified SV40-based vectors have also been very promising. The future of gene therapy will probably entail using an array of gene delivery vehicles, each with its own strengths and weaknesses. The vector systems will probably be as diverse as the applications to which they will be put.

Journal Article↗
PubMed1983

Mutations in the major DNA-binding protein gene of herpes simplex virus type 1 result in increased levels of viral gene expression.

We have examined the effect of temperature-sensitive mutations in the herpes simplex virus 1 DNA-binding protein gene on viral gene expression. We have found that at the nonpermissive temperature, the synthesis of certain immediate early, early, and late viral polypeptides was greater in cells infected with the temperature-sensitive mutants than in cells infected with the wild-type virus. This effect was independent of the requirement for this viral protein for viral DNA replication. The altered rate of synthesis of viral proteins was due to a thermolabile gene product. Cells infected with these mutants at the permissive temperature and then shifted to the nonpermissive temperature exhibited enhanced levels of viral gene expression. The addition of actinomycin D at the time of the temperature shift prevented the alteration in viral protein synthesis. Therefore, continuing transcription is required for this change in gene expression. Northern blot analysis of cytoplasmic RNA showed that the steady-state level of specific viral transcripts expressed from parental virus genomes was greater in cells infected by these mutants at the nonpermissive temperature. These results indicate that the major DNA-binding protein of herpes simplex virus type 1 acts as a negative regulator of viral gene expression by affecting the abundance of cytoplasmic viral mRNAs.

Animals↗
PubMedDate not supplied

Efficient gene transfer and expression in islets by an adenoviral vector that lacks all viral genes.

Although adenoviral vector-mediated gene transfer has significant potential for gene therapy, host immune responses to virally expressed proteins and small insert capacity may limit its clinical application. In order to overcome these disadvantages, a new adenoviral vector that lacks all viral genes has been developed. Using the green fluorescent (GFP) gene as a reporter gene, we investigated the efficiency of gene transfer by this all-viral-genes-deleted and minimal cis-element remaining adenoviral vector (miniAd-GFP) in islets in vitro and ex vivo, and compared it with the E1-deleted adenoviral vector (E1-GFP). One day after in vitro infection, GFP was expressed in both miniAd-GFP- and E1-GFP-infected islets. The percentage of GFP-positive single cells was not significantly different between miniAd-GFP-infected islets and E1-GFP-infected islets. When these islets were transplanted into syngeneic diabetic mice, both miniAd-GFP- and E1-GFP-infected islet grafts reversed diabetes, and normal blood glucose levels were maintained for over 20 weeks posttransplantation. Mild lymphocyte infiltration was found in all E1-GFP-infected islet grafts at all time points. However, this was not seen in most miniAd-GFP-infected islet grafts. Our results indicate that gene transfer by an adenoviral vector that lacks all viral genes is as efficient as E1-deleted adenoviral vector-mediated gene transfer in islets. Furthermore, this adenoviral vector might be less immunogeneic than the E1-deleted adenoviral vector.

Adenoviridae↗
PubMed2002

Gene-viral vectors: a promising way to target tumor cells and express anticancer genes simultaneously.

OBJECTIVE: To develop a new kind of vector system called gene-viral vector, which combines the advantages of gene and virus therapies. METHODS: Using recombinant technology, an anti-tumor gene was inserted into the genome of replicative virus specific for tumor cells. The cell killing effect, reporter gene expression of the green fluorescence protein, anti-tumor gene expression of mouse interleukin-12 (mIL-12) and replication of virus were observed by the methods of cell pathology, fluorescence microscopy, ELISA and electron microscopy, respectively. RESULTS: A new kind of gene-viral vector system of adenovirus, in which the E1b-55 kD gene was deleted but the E1a gene was preserved, was constructed. The vector system, like the replicative virus ONYX-015, replicated and proliferated in tumor cells but not in normal ones. Our vector had an advantage over ONYX-015 in that it carried different kinds of anti-tumor genes to enhance its therapeutic effect. The reporter gene expression of the green fluorescence protein in tumor cells was much better than the adenovirus vector employed in conventional gene the rapy, and the expression in our vector system was as low as or even less than that in the conventional adenovirus gene therapy system. Similar results were observed in experiments with this vector system carrying the anti-tumor gene mIL-12. Replication and proliferation of the virus carrying the mIL-12 gene in tumor cells were confirmed by electron microscopy. CONCLUSIONS: Gene-viral vectors are new vectors with an anti-tumor gene inserted into the genome of replicative virus specific for tumor cells. Because of the specific replication and proliferation of the virus in tumor cells, expression of the anti-tumor gene is increased hundreds to thousands of times. This approach takes full advantages of gene therapy and virus therapy to enhance the effect on the tumor. It overcomes the disadvantages of conventional gene therapy, such as low transfer rate, low gene expression, lack of target tropism, and low anti-tumor activity. We believe that this is a promising means for future tumor treatment.

Adenoviridae↗