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At least 829 records · Page 46Linked to original sources
PubMed2001

Small tumor virus genomes are integrated near nuclear matrix attachment regions in transformed cells.

More than 15% of human cancers have a viral etiology. In benign lesions induced by the small DNA tumor viruses, viral genomes are typically maintained extrachromosomally. Malignant progression is often associated with viral integration into host cell chromatin. To study the role of viral integration in tumorigenesis, we analyzed the positions of integrated viral genomes in tumors and tumor cell lines induced by the small oncogenic viruses, including the high-risk human papillomaviruses, hepatitis B virus, simian virus 40, and human T-cell leukemia virus type 1. We show that viral integrations in tumor cells lie near cellular sequences identified as nuclear matrix attachment regions (MARs), while integrations in nonneoplastic cells show no significant correlation with these regions. In mammalian cells, the nuclear matrix functions in gene expression and DNA replication. MARs play varied but poorly understood roles in eukaryotic gene expression. Our results suggest that integrated tumor virus genomes are subject to MAR-mediated transcriptional regulation, providing insight into mechanisms of viral carcinogenesis. Furthermore, the viral oncoproteins serve as invaluable tools for the study of mechanisms controlling cellular growth. Similarly, our demonstration that integrated viral genomes may be subject to MAR-mediated transcriptional effects should facilitate elucidation of fundamental mechanisms regulating eukaryotic gene expression.

Attachment Sites, Microbiological↗
PubMed2001

DNase protection analysis of retrovirus integrase at the viral DNA ends for full-site integration in vitro.

Retrovirus intasomes purified from virus-infected cells contain the linear viral DNA genome and integrase (IN). Intasomes are capable of integrating the DNA termini in a concerted fashion into exogenous target DNA (full site), mimicking integration in vivo. Molecular insights into the organization of avian myeloblastosis virus IN at the viral DNA ends were gained by reconstituting nucleoprotein complexes possessing intasome characteristics. Assembly of IN-4.5-kbp donor complexes capable of efficient full-site integration appears cooperative and is dependent on time, temperature, and protein concentration. DNase I footprint analysis of assembled IN-donor complexes capable of full-site integration shows that wild-type U3 and other donors containing gain-of-function attachment site sequences are specifically protected by IN at low concentrations (<20 nM) with a defined outer boundary mapping ~20 nucleotides from the ends. A donor containing mutations in the attachment site simultaneously eliminated full-site integration and DNase I protection by IN. Coupling of wild-type U5 ends with wild-type U3 ends for full-site integration shows binding by IN at low concentrations probably occurs only at the very terminal nucleotides (<10 bp) on U5. The results suggest that assembly requires a defined number of avian IN subunits at each viral DNA end. Among several possibilities, IN may bind asymmetrically to the U3 and U5 ends for full-site integration in vitro.

Attachment Sites, Microbiological↗
PubMed2002

Differential requirements for activation of integrated and transiently transfected human T-cell leukemia virus type 1 long terminal repeat.

Adult T-cell leukemia (ATL) cells contain integrated human T-cell leukemia virus type 1 (HTLV-1) proviruses. Although the exact sequence of events leading to the development of ATL remains incompletely resolved, expression of the integrated HTLV-1 long terminal repeat (LTR) is likely required at some point during the process of T-cell transformation. While much has been learned about the regulated expression of transiently transfected LTR reporter plasmids, an analysis of factors required for expression of chromosomally integrated HTLV-1 LTR has not been done. Here, we have constructed CHOK1 and HeLa cells that contain an integrated HTLV-1 LTR-luciferase gene. Using these cells, we have compared the requirements for activation of transiently transfected versus stably integrated HTLV-1 LTR. We observed different requirements for CREB, p300, and P/CAF in the expression of transiently transfected versus stably integrated HTLV-1 LTR. Furthermore, with dominant-negative mutants of CREB, p300, and P/CAF, we found that activation of integrated HTLV-1 LTR by an ambient stress signal, UV-C, proceeds through a path mechanistically distinct from that used by viral oncoprotein, Tax. Our findings point to additional complexities in the regulated expression of HTLV-1 proviruses compared with those hitherto revealed through transfection studies.

Acetyltransferases↗
PubMed2004

Analysis of integration sites of Jaagsiekte sheep retrovirus in ovine pulmonary adenocarcinoma.

Ovine pulmonary adenocarcinoma (OPA) is an infectious lung tumor of sheep caused by Jaagsiekte sheep retrovirus (JSRV). To test the hypothesis that JSRV insertional mutagenesis is involved in the oncogenesis of OPA, we cloned and characterized 70 independent integration sites from 23 cases of OPA. Multiple integration sites were identified in most tumors. BLAST analysis of the sequences did not disclose any potential oncogenic motifs or any identical integration sites in different tumors. Thirty-seven of the integration sites were mapped to individual chromosomes by PCR with a panel of sheep-hamster hybrid cell lines. Integration sites were found on 20 of the 28 sheep chromosomes, suggesting a random distribution. However, four integration sites from four different tumors mapped to chromosome 16. By Southern blot hybridization, probes derived from two of these sites mapped to within 5 kb of each other on normal sheep DNA. These sites were found within a single sheep bacterial artificial chromosome clone and were further mapped to only 2.5 kb apart, within an uncharacterized predicted gene and less than 200 kb from a mitogen-activated protein kinase-encoding gene. These findings suggest that there is at least one common integration site for JSRV in OPA and add weight to the hypothesis that insertional mutagenesis is involved in the development of this tumor.

Animals↗
PubMed2005

A capsid-modified helper-dependent adenovirus vector containing the beta-globin locus control region displays a nonrandom integration pattern and allows stable, erythroid-specific gene expression.

Gene therapy for hemoglobinopathies requires efficient gene transfer into hematopoietic stem cells and high-level erythroid-specific gene expression. Toward this goal, we constructed a helper-dependent adenovirus vector carrying the beta-globin locus control region (LCR) to drive green fluorescent protein (GFP) expression, whereby the LCR-GFP cassette is flanked by adeno-associated virus (AAV) inverted terminal repeats (Ad.LCR-beta-GFP). This vector possesses the adenovirus type 35 fiber knob that allows efficient infection of hematopoietic cells. Transduction and vector integration studies were performed in MO7e cells, a growth factor-dependent CD34(+) erythroleukemic cell line, and in cord blood-derived human CD34(+) cells. Stable transduction of MO7e cells with Ad.LCR-beta-GFP was more efficient and less subject to position effects and silencing than transduction with a vector that did not contain the beta-globin LCR. Analysis of integration sites indicated that Ad.LCR-beta-GFP integration in MO7e cells was not random but tethered to chromosome 11, specifically to the globin LCR. More than 10% of analyzed integration sites were within the chromosomal beta-globin LCR. None of the Ad.LCR-beta-GFP integrations occurred in exons. The integration pattern of a helper-dependent vector that contained X-chromosomal stuffer DNA was different from that of the beta-globin LCR-containing vector. Infection of primary CD34(+) cells with Ad.LCR-beta-GFP did not affect the clonogenic capacity of CD34(+) cells. Transduction of CD34(+) cells with Ad.LCR-beta-GFP resulted in vector integration and erythroid lineage-specific GFP expression.

Adenoviridae↗
PubMed2005

Integration targeting by avian sarcoma-leukosis virus and human immunodeficiency virus in the chicken genome.

We have analyzed the placement of sites of integration of avian sarcoma-leukosis virus (ASLV) and human immunodeficiency virus (HIV) DNA in the draft chicken genome sequence, with the goals of assessing species-specific effects on integration and allowing comparison to the distribution of chicken endogenous retroviruses (ERVs). We infected chicken embryo fibroblasts (CEF) with ASLV or HIV and sequenced 863 junctions between host and viral DNA. The relationship with cellular gene activity was analyzed by transcriptional profiling of uninfected or ASLV-infected CEF cells. ASLV weakly favored integration in active transcription units (TUs), and HIV strongly favored active TUs, trends seen previously for integration in human cells. The ERVs, in contrast, accumulated mostly outside TUs, including ERVs related to ASLV. The minority of ERVs present within TUs were mainly in the antisense orientation; consequently, the viral splicing and polyadenylation signals would not disrupt cellular mRNA synthesis. In contrast, de novo ASLV integration sites within TUs showed no orientation bias. Comparing the distribution of de novo ASLV integration sites to ERVs indicated that purifying selection against gene disruption, and not initial integration targeting, probably determined the ERV distribution. Further analysis indicated that ERVs in humans, mice, and rats showed similar distributions, suggesting purifying selection dictated their distributions as well.

Alpharetrovirus↗
PubMed2006

Human immunodeficiency virus type 1 incorporated with fusion proteins consisting of integrase and the designed polydactyl zinc finger protein E2C can bias integration of viral DNA into a predetermined chromosomal region in human cells.

In vitro studies using fusion proteins consisting of human immunodeficiency virus type 1 integrase (IN) and a synthetic polydactyl zinc finger protein E2C, a sequence-specific DNA-binding protein, showed that integration of retroviral DNA can be biased towards a contiguous 18-bp E2C-recognition site. To determine whether the fusion protein strategy can achieve site-specific integration in vivo, viruses were prepared by cotransfection and various IN-E2C fusion proteins were packaged in trans into virions. The resulting viruses incorporated with the IN-E2C fusion proteins were functional and capable of performing integration at a level ranging from 1 to 24% of that of viruses containing wild-type (WT) IN. Two of the more infectious viruses, which contained E2C fused to either the N (E2C/IN) or to the C (IN/E2C) terminus of IN, were tested for their ability to direct integration into a unique E2C-binding site present within the 5' untranslated region of erbB-2 gene on human chromosome 17. The copy number of proviral DNA was measured using a quantitative real-time nested-PCR assay, and the specificity of directed integration was determined by comparing the number of proviruses within the vicinity of the E2C-binding site to that in the whole genome. Viruses containing IN/E2C fusion proteins had sevenfold higher preference for integrating near the E2C-binding site than those viruses containing WT IN, whereas viruses containing E2C/IN had 10-fold higher preference. The results indicated that the IN-E2C fusion protein strategy is capable of directing integration of retroviral DNA into a predetermined chromosomal region in the human genome.

Binding Sites↗
PubMed1992

Genetics of retroviral integration.

Today the retroviral integration reaction is probably understood, both in terms of its genetics and chemistry, in as much detail as any eukaryotic recombination process. That understanding is in part due to its high efficiency (for it can be induced to occur synchronously in every cell of a culture); to its simplicity (for there is only one major protein player); to its accessibility (for the viral genome has provided all the cis- and trans-acting players); and to its willingness to perform well in vitro, ultimately with purified components. The process has thus made the classic transition from a phenomenon to be studied genetically to a reaction that can also be studied biochemically. The next advances in our understanding of the process of retroviral integration are likely to center on chemical issues. Some basic enzymological issues need to be addressed: we need to determine the oligomeric state of the native IN protein; its state when bound to linear viral DNA; the residues at the active site; the residues involved in sequence-specific recognition of DNA; and the points of contact between IN monomers. Much of this information will follow from detailed mutagenesis of expressed IN genes. A crucial step will be the determination of the structure of the IN protein at atomic resolution through X-ray diffraction analysis of protein crystals, a project underway in several laboratories. That structure may immediately suggest how the enzyme contacts and joins two DNA molecules, and will enormously facilitate the design and interpretation of mutational studies. It seems plausible that we can understand the IN protein as a machine as well as any nuclease or recombinase. A significant number of larger biological questions about integration remain unanswered and will require genetic approaches. What is the true structure of the preintegration complex in the cytoplasm? How does the complex enter the nucleus, and obtain access to the host DNA? Why, at least for most viruses in most cells, does integration depend on cell division? Why does efficient expression of the viral DNA to form progeny viral RNA and proteins depend on integration? How are target sites for integration on the host genome selected, and why are there "hot spots" for insertion? Are there host proteins that facilitate or participate in the integration reaction itself, and what are those proteins? Are any of those proteins involved in site selection?(ABSTRACT TRUNCATED AT 400 WORDS)

DNA Mutational Analysis↗
PubMed2004

Systematic review of genomic integration sites of human papillomavirus genomes in epithelial dysplasia and invasive cancer of the female lower genital tract.

Cancers of the anogenital tract as well as some head and neck cancers are caused by persistent infections with high-risk type human papillomaviruses (HPVs). Two viral oncogenes, E6 and E7, induce severe chromosomal instability associated with centrosome aberrations, anaphase bridges, chromosome lagging, and breaking. This occurs early in preneoplastic lesions, when the viral genome still persists in an episomal state. In most invasive cancers and also in a few high-grade dysplastic lesions, however, integration of high-risk HPV genomes into the host genome is observed. Integration seems to be a direct consequence of chromosomal instability and an important molecular event in the progression of preneoplastic lesions. Disruption or deregulation of defined critical cellular gene functions by insertional mutagenesis by integrated HPV genome fragments has been hypothesized as one major promoting factor in the pathogenesis of HPV-associated cancers. This hypothesis was based on the detection of HPV integration events in the area of tumor-relevant genes in few cases. Here, we reviewed >190 reported integration loci with respect to changes in the viral structure and the targeted genomic locus. This analysis confirms that HPV integration sites are randomly distributed over the whole genome with a clear predilection for genomic fragile sites. No evidence for targeted disruption or functional alteration of critical cellular genes by the integrated viral sequences could be found.

Cell Transformation, Viral↗
PubMed2004

HIV-1 gene expression: lessons from provirus and non-integrated DNA.

Replication of HIV-1 involves a series of obligatory steps such as reverse transcription of the viral RNA genome into double-stranded DNA, and subsequent integration of the DNA into the human chromatin. Integration is an essential step for HIV-1 replication; yet the natural process of HIV-1 infection generates both integrated and high levels of non-integrated DNA. Although proviral DNA is the template for productive viral replication, the non-integrated DNA has been suggested to be active for limited viral gene synthesis. In this review, the regulation of viral gene expression from proviral DNA will be summarized and issues relating to non-integrated DNA as a template for transcription will be discussed, as will the possible function of pre-integration transcription in HIV-1 replication cycle.

Animals↗
PubMed2006

Integrated service networks: the Quebec case.

In the current context of health-care reform, integrated service networks are presented as main solutions to enhance efficiency. During the past few years, there has been an abundance of literature focusing on integration and the underlying implementation issues. However, the concept of integrated service networks remains fluid, and there are few typologies on health-care inter-organizational relations. The Quebec health-care system offers fertile ground for furthering our understanding of this concept because of its public system of funding, its integration of health and social missions, and the present reform's state of development. On the basis of a review of the literature and empirical studies, this article intends to clarify the concept of integrated service networks. A typology of inter-organizational relations and the main parameters for organizing integrated service networks are presented. The article also discusses the effectiveness of integration models.

Community Mental Health Services↗
PubMed2005

Quantification of HFV-integrated DNA in human cells by Alu-LTR real-time PCR.

Integration is described as a key step in viral replication of all retroviruses. A sensitive and quantitative measure of an integrated molecule is a good way to examine the importance of the integration step and to evaluate efficiency of retroviral vectors for gene transfer or anti-integrase drugs. Here, we report a sensitive and quantitative real-time polymerase chain reaction (PCR) technique to measure integrated viral DNA in human cells during a foamy virus (HFV) infection. This technique is based on two steps of PCR. The first round amplifies Alu-LTR (long terminal repeat) sequences resulting from viral integration. The second round of PCR is performed to quantify these events of integration. Quantification is monitored by the comparison of the amplification curve of the sample against a standard scale constituted of viral DNA from chronically infected cells. Sensitivity of this technique allows us to detect as few as 25 copies of HFV-integrated DNA in 50,000 cells.

Alu Elements↗
PubMed2000

Putting it all together: improving display integration in ecological displays.

Computer displays are being designed for increasingly larger industrial systems. As the application domain scales up, maintaining integration across different kinds of views becomes more challenging. This paper presents the results of a study of three different approaches to integration based on the spatial and temporal proximity of related information objects. The domain used for evaluation was a simulation of an industry-scale conventional power plant. All three displays were ecological displays developed using an abstraction hierarchy analysis. Views were integrated in a high-space/low-time, low-space/high-time, and high-space/high-time integration of means-end related objects. During a fault detection and diagnosis task, it was found that a low level of integration, high-space/ low-time, provided the fastest fault detection time. However, the most integrated condition, high-space/high-time, resulted in the fastest and most accurate fault diagnosis performance. Actual or potential applications of this research include computer displays for large-scale systems such as network management or process control, for which problem solving is critical and integration must be maintained.

Adult↗
PubMed2004

Leprosy control strategies and the integration of health services: an international perspective.

Integration of leprosy services into the general health services is regarded as the core strategy to ensure that leprosy control remains cost-effective and equitable, and, thus, sustainable in the coming years. In this article an extensive review is presented of the integration of leprosy services into the general health services. After the rationale of integration is discussed, the article highlights several recent developments within leprosy control and the health sector that are in support of the integration process. An overview is presented of recent experiences in countries that have already embarked on the integration process. Based on these experiences important lessons can be learned and incorporated into a model for the process of integration. This model, which is presented at the end of the article, will assist countries to successfully integrate leprosy services into the general health services.

Brazil↗
PubMed2006

Achieving maximum ROI from corporate databases: exploiting your databases with integrated querying for better decision-making.

In order to increase the rate of drug discovery, pharmaceutical and biotechnology companies spend billions of dollars a year assembling research databases. Current trends still indicate a falling rate in the discovery of New Molecular Entities (NMEs). It is widely accepted that the data need to be integrated in order for it to add value. The degree to which this must be achieved is often misunderstood. The true goal of data integration must be to provide accessible knowledge. If knowledge cannot be gained from these data, then it will invalidate the business case for gathering it. Current data integration solutions focus on the initial task of integrating the actual data and to some extent, also address the need to allow users to access integrated information. Typically the search tools that are provided are either restrictive forms or free text based. While useful, neither of these solutions is suitable for providing full coverage of large numbers of integrated structured data sources. One solution to this accessibility problem is to present the integrated data in a collated manner that allows users to browse and explore it and also perform complex ad-hoc searches on it within a scientific context and without the need for advanced Information Technology (IT) skills. Additionally, the solution should be maintainable by 'in-house' administrators rather than requiring expensive consultancy. This paper examines the background to this problem, investigates the requirements for effective exploitation of corporate data and presents a novel effective solution.

Databases, Factual↗
PubMed2004

Human cell proteins and human immunodeficiency virus DNA integration.

Integration, catalyzed by the viral integrase (IN) protein, is a crucial step in the life cycle of all retroviruses including human immunodeficiency virus type 1 (HIV-1). Although purified HIV-1 IN protein is sufficient to catalyze the DNA breakage and joining steps of integration in the absence of any other protein factor, a number of studies indicate that cellular proteins participate in the integration process in cells. These host cell proteins have been proposed to act through binding the pre-integrated viral cDNA substrate, by directly interacting with the IN protein, and/or by repairing the single-stranded DNA gaps that occur at viral/chromosomal DNA junctions during integration. In this paper we summarize the identification and potential roles of specific cell factors in HIV-1 integration. We also present experimental results of human cell proteins that coimmunoprecipitated with HIV-1 IN following its expression in HeLa cells and discuss these results in light of the previously-identified integration cofactors.

Animals↗
PubMed1997

Clinical indications of multiple integrations of human T-cell lymphotropic virus type I proviral DNA in adult T-cell leukemia/lymphoma.

In this review, we discuss the possible relationship between the clinical characteristics and the multiple integration of human T-cell lymphotropic virus type I (HTLV-I) proviral DNA in patients with adult T-cell leukemia/lymphoma (ATL). Some patients with ATL show multiple HTLV-I integrations and exhibit clinical characteristics unlike those of ATL patients who show the typical integration of a single provirus. Multiple HTLV-I integrations can be detected by Southern blotting as multiple bands having varied intensities. These multiple integration conditions can arise from one tumor cell clone carrying multiple copies of the provirus, or from multiple cell clones, each carrying one copy of the provirus. The former patients manifest an extremely aggressive clinical course with the infiltration of unusual organs such as the retina and uvea. The latter patients show an indolent clinical course with skin lesions. These findings suggest that the clinical implications for multiple HTLV-I integrations exist in ATL. This may be one of the explanations for the heterogeneous findings in the disease. Such observations may provide information linking viral integration with clinical manifestations, and improve our understanding of the pathogenesis of ATL.

DNA, Viral↗
PubMed1998

Sites of recombinant adeno-associated virus integration.

Adeno-associated virus (AAV), a defective parvovirus, is considered a promising vector for the delivery of therapeutic genes to cells. Both wild-type and recombinant AAV display a wide tropism and integrate into the host genome, in the absence of helper virus, establishing a latent infection. A unique characteristic of wild-type AAV and a potential advantage for use as a delivery system for gene therapy is the site-specific integration of wild-type virus within a small region of chromosome 19, 19q13.3-qter (AAVS1), in up to 85% of cell lines infected with the virus. Although recombinant AAVs, containing only the inverted terminal repeats of wild-type virus, can integrate efficiently into the host genome, specificity for the AAVS1 site appears to be lost. To address this question, the integration characteristics of two recombinant AAVs lacking the rep and cap genes in HeLa cells were examined. Analysis of Southern blots indicated that none of twenty-six cell clones generated after infection with either one of the recombinant AAVs demonstrated integration within the AAVS1 locus on chromo-some 19. Analysis of five of the cell lines by fluorescent chromosome in situ hybridization confirmed the loss of chromosome 19 specificity. Each integration site mapped near a known fragile site and/or location of a proto-oncogene or growth regulatory gene. Retention of site-specific integration of wild-type AAV will require the inclusion of additional AAV-specific sequences within the recombinant vectors.

Dependovirus↗