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Results for “Virus Integration”

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At least 541 records · Page 30Linked to original sources
PubMed2004

The peripheral cannabinoid receptor Cb2, frequently expressed on AML blasts, either induces a neutrophilic differentiation block or confers abnormal migration properties in a ligand-dependent manner.

Cb2, the gene encoding the peripheral cannabinoid receptor, is located in a common virus integration site and is overex-pressed in retrovirally induced murine myeloid leukemias. Here we show that this G protein-coupled receptor (GPCR) is also aberrantly expressed in a high percentage of human acute myeloid leukemias. We investigated the mechanism of transformation by Cb2 and demonstrate that aberrant expression of this receptor on hematopoietic precursor cells results in distinct effects depending on the ligand used. Cb2-expressing myeloid precursors migrate upon stimulation by the endocannabinoid 2-arachidonoylglycerol and are blocked in neutrophilic differentiation upon exposure to another ligand, CP55940. Both effects depend on the activation of G(alphai) proteins and require the mitogen-induced extracellular kinase/extracellular signal-regulated kinase (MEK/ERK) pathway. Down-regulation of cyclic adenosine monophosphate (cAMP) levels upon G(alphai) activation is important for migration induction but is irrelevant for the maturation arrest. Moreover, the highly conserved G protein-interacting DRY motif, present in the second intracellular loop of GPCRs, is critical for migration but unimportant for the differentiation block. This suggests that the Cb2-mediated differentiation block requires interaction of G(alphai) proteins with other currently unknown motifs. This indicates a unique mechanism by which a transforming GPCR, in a ligand-dependent manner, causes 2 distinct oncogenic effects: altered migration and block of neutrophilic development.

Acute Disease↗
PubMed2006

Latency: the hidden HIV-1 challenge.

Eradication of HIV-1 from an infected individual cannot be achieved by current regimens. Viral reservoirs established early during the infection remain unaffected by anti-retroviral therapy for a long time and are able to replenish systemic infection upon interruption of the treatment. Therapeutic targeting of viral latency will require a better understanding of the basic mechanisms underlying the establishment and long-term maintenance of HIV-1 in resting memory CD4 T cells, the most prominent reservoir of transcriptionally silent provirus. Since the molecular mechanisms that permit long term transcriptional control of proviral gene expression in these cells are still obscure, this review aims at summarizing the various aspects of the problem that need to be considered. In particular, this review will focus the attention on the control of transcription imposed by chromatin through various epigenetic mechanisms. Exploring the molecular details of viral latency will provide new insights for eventual future therapeutics that aim at viral eradication.

Animals↗
PubMed2004

Gene therapy in animal models of rheumatoid arthritis: are we ready for the patients?

Rheumatoid arthritis (RA) is a chronic inflammatory disease of the synovial joints, with progressive destruction of cartilage and bone. Anti-tumour necrosis factor-alpha therapies (e.g. soluble tumour necrosis factor receptors) ameliorate disease in 60-70% of patients with RA. However, the need for repeated systemic administration of relatively high doses in order to achieve constant therapeutic levels in the joints, and the reported side effects are downsides to this systemic approach. Several gene therapeutic approaches have been developed to ameliorate disease in animal models of arthritis either by restoring the cytokine balance or by genetic synovectomy. In this review we summarize strategies to improve transduction of synovial cells, to achieve stable transgene expression using integrating viruses such as adeno-associated viruses, and to achieve transcriptionally regulated expression so that drug release can meet the variable demands imposed by the intermittent course of RA. Evidence from animal models convincingly supports the application of gene therapy in RA, and the feasibility of gene therapy was recently demonstrated in phase I clinical trials.

Animals↗
PubMed2001

Zebrafish Meis functions to stabilize Pbx proteins and regulate hindbrain patterning.

Homeodomain-containing Hox proteins regulate segmental identity in Drosophila in concert with two partners known as Extradenticle (Exd) and Homothorax (Hth). These partners are themselves DNA-binding, homeodomain proteins, and probably function by revealing the intrinsic specificity of Hox proteins. Vertebrate orthologs of Exd and Hth, known as Pbx and Meis (named for a myeloid ecotropic leukemia virus integration site), respectively, are encoded by multigene families and are present in multimeric complexes together with vertebrate Hox proteins. Previous results have demonstrated that the zygotically encoded Pbx4/Lazarus (Lzr) protein is required for segmentation of the zebrafish hindbrain and proper expression and function of Hox genes. We demonstrate that Meis functions in the same pathway as Pbx in zebrafish hindbrain development, as expression of a dominant-negative mutant Meis results in phenotypes that are remarkably similar to that of lzr mutants. Surprisingly, expression of Meis protein partially rescues the lzr(-) phenotype. Lzr protein levels are increased in embryos overexpressing Meis and are reduced for lzr mutants that cannot bind to Meis. This implies a mechanism whereby Meis rescues lzr mutants by stabilizing maternally encoded Lzr. Our results define two functions of Meis during zebrafish hindbrain segmentation: that of a DNA-binding partner of Pbx proteins, and that of a post-transcriptional regulator of Pbx protein levels.

Animals↗
PubMed1991

Generation of functional murine macrophage lines employing a helper-free and replication-defective SV40-retrovirus: cytokine-dependent growth.

By using a helper-free and replication-defective recombinant retrovirus encoding the SV40 early antigens (MV40), we have established continuous macrophage (M phi) lines. All of the lines were nonproducer M phi's with differentiated M phi functions such as phagocytosis, cytotoxicity, and IL-1 and TNF production. To determine the effects of several cytokines on growth of mature M phi's, the responsiveness of these established M phi lines to various cytokines was investigated in methylcellulose culture. Their response patterns to several cytokines alone and in combination were different, implying that there might be mature M phi subpopulations with distinct growth profiles regulated by several cytokines. On the other hand, all of the lines efficiently yielded a number of colonies in response to interleukin-4 (IL-4) alone. Moreover, IL-4 cooperated with interleukin-3 (IL-3) to enhance colony formation of all the lines. A similarly synergistic effect was observed in combination of IL-4 and macrophage-colony stimulating factor (M-CSF) in almost all the lines. Similar results were obtained with colony formation of fresh thioglycolate-induced M phi's. These observations suggested that IL-4 was involved in growth of mature M phi's. Our present results suggest that the helper-free and replication-defective MV40 is of use to obtain continuous and functional cell lines from primary M phi's.

Animals↗
PubMed2004

Gene transfer by retroviral vectors: an overview.

Viruses have evolved to deliver their genetic cargo to cells and, due to the pathogenicity of some viruses, this process has been the subject of a great deal of study. In this respect, retroviruses came to the fore in the early 1900s with the demonstration by Ellermann and Bang and by Rous that chicken leukosis was caused by a virus, now referred to as avian sarcoma/leukosis virus (ASLV). This began a body of work that led to the identification of virus-induced tumors in mammalian species and retroviruses (as they are now called) were identified as the causative agents for a number of pathologies from tumors to acquired immunodefiencey syndrome (AIDS). Retroviruses were characterized as RNA viruses that replicate through a DNA intermediate. The study of retroviruses contributed and led to the elucidation of a number of diverse biological phenomena as the oncogenes carried by these viruses began to be identified as receptors, kinases, and transcription factors (3). The idea that these viruses could be used to ferry a gene of choice, rather than the viral genome, springs from the study of Rous sarcoma virus (RSV).

Animals↗
PubMed2004

Production of recombinant proteins: challenges and solutions.

Efficient strategies for the production of recombinant proteins are gaining increasing importance, as more applications that require high amounts of high-quality proteins reach the market. Higher production efficiencies and, consequently, lower costs of the final product are needed for obtaining a commercially viable process. In this chapter, common problems in recombinant protein production are reviewed and strategies for their solution are discussed. Such strategies include molecular biology techniques, as well as manipulation of the culture environment. Finally, specific problems relevant to different hosts are discussed.

Bioreactors↗
PubMed1994

Chromosome fragility and instability in human cancer.

The development of cancer is a multistep process triggered by physical, chemical, or biological carcinogenic factors, with the progression to an invasive phenotype requiring cumulative genetic alterations. Not all cellular genomic sequences are equally susceptible to carcinogenic factors or involved in pathologically relevant genetic alterations. Because of structural chromatin organization and DNA replication, certain genomic regions exhibit an increased fragility and tendency to recombination. At these regions, called fragile sites, there is a convergence of specific deletions, translocations, chemically induced lesions, and virus integrations. Isolation and cloning of sequences at fragile sites are important to a better understanding of the carcinogenesis process and to development of preventive measures.

Chromosome Fragile Sites↗
PubMed2006

Establishment and characterization of a clonal human extraskeletal Ewing's sarcoma cell line, EES1.

Ewing's sarcoma, a small round cell sarcoma arising in soft tissue as well as the bone, is one of the most malignant tumors in children and young adults. Few established cell lines of extraskeletal Ewing's sarcoma (EES) have been reported, which made it difficult to examine the biological features of EES. Therefore, we have established a new clonal cell line of EES. We report its morphological characters, results of chromosomal and immunohistochemical analysis. A piece of tumor obtained from the 18-year-old female patient with EES was xenografted in a nude mouse. In vitro subcultured cells were then obtained from this xenograft. A clonal cell line was subsequently established by limiting dilution and designated EES1. EES1 cells had a doubling time of 24 hours. In the xenografted tumor, the cells expressed vimentin, CD99 (MIC2), neuron specific enolase (NSE) and cytokeratin. The original tumor cells also expressed vimentin, CD 99, and NSE, but was negative for cytokeratin. The morphological and immunohistochemical features of this cell line established, except for cytokeratin expression, were consistent with those of the primary tumor. Cytogenetic analysis of EES1 revealed chromosomal translocation of t(11; 12)(q24;ql2). The chimeric fusion of the Ewing's sarcoma gene in band 22q12 with the Friend leukemia virus integration-1 gene in band 11q24 was also demonstrated. Fluorescence in situ hybridization further confirmed the presence of translocation involving the Ewing's sarcoma gene in both the primary tumor and EES1 cells. In conclusion, we have established a human EES cell line EES1, which will provide a useful model for studying various aspects of human EES.

Adolescent↗
PubMed2003

Zonal expression of dickkopf-3 and components of the Wnt signalling pathways in the human adrenal cortex.

The mechanisms underlying the differentiation of the adrenal cortex into zones are unclear. Microarray studies on RNA from microdissected zona reticularis (ZR) and zona fasciculata/zona glomerulosa (ZF/ZG) derived from adult human adrenal glands showed that a gene of the dickkopf family (DKK), DKK3, is differentially expressed in the zones. The Dickkopf proteins are morphogens involved in Wnt signalling. Northern blotting showed higher DKK3 transcript levels in ZF/ZG than ZR samples. In situ hybridization on adult human adrenal gland sections showed that DKK3 expression was much higher in the ZG than in the ZF or ZR. DKK3 expression was also higher in the medulla. We screened for expression of other members of the DKK family and the related Wingless-type mouse mammary tumor virus integration site gene family (WNT), frizzled (FZD), and dishevelled (DVL) gene families. Among dickkopf family members, only DKK3 was expressed at a detectable level in both human and mouse adrenocortical RNA samples. Consistent with previously published data on the effects of Wnt4 gene disruption in the mouse, we found only WNT4 expression within the WNT family in both human and mouse RNA. Northern blotting showed that WNT4 was expressed at a higher level in ZF/ZG cells than in ZR. The higher level of DKK3 and WNT4 expression in ZF/ZG cells was confirmed by real-time PCR. In the frizzled and dishevelled families we found FZD1, FZD2 and DVL3 transcripts in human adrenocortical RNA, and FZD2 and DVL3 in mouse adrenocortical RNA. These data show that a variety of genes of the Wnt signalling pathways are expressed in the adrenal cortex. The zonal distribution of DKK3 expression suggests that it could be involved in zonal differentiation or growth.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Electroporation of proviral RCAS DNA alters gene expression in the embryonic chick hindbrain.

Gene transfer by means of electroporation is an effective method for delivering DNA into cells. Expression vectors encoding green fluorescent protein (GFP) are routinely used as a control for this technique and are also regularly used to indirectly or directly monitor the expression of introduced transgenes. However, recent studies suggest that GFP may have nonspecific and/or cytotoxic side effects. In this study, we investigated the effects of enhanced GFP (EGFP) expression delivered by means of electroporation of proviral RCASBP(B)-EGFP DNA on gene expression in the hindbrain of chick embryos. We examined, via whole-mount in situ hybridization, the expression of a number of transcription factors. We found that Tlx-1 was ectopically expressed following electroporation of proviral RCASBP(B)-EGFP DNA. In contrast, the number of cells expressing Tlx-3, Phox2a, and Phox2b were reduced. Intriguingly, these effects could be mimicked by electroporation of wild-type proviral RCASBP(B) DNA (i.e., lacking the GFP insert). However, neither delivery of the EGFP transgene by means of viral infection nor electroporation alone yielded aberrant expression patterns. Together our data indicate that alterations of gene expression patterns are not directly due to the expression of EGFP but instead reflect a confounding effect of electroporating proviral DNA.

Animals↗
PubMed2003

Stages of HIV replication and targets for therapeutic intervention.

The replication cycle of human immunodeficiency virus (HIV) is divided into an early and a late phase. Most of the steps of the cycle have been targeted in antiviral therapy, although the drugs currently available for clinical use are only effective against two replication enzymes of the virus, either against the reverse transcriptase or against the viral protease. The introduction of combination anti-retroviral therapy changed the prognosis of HIV infection. HIV-related morbidity and mortality rates in patients with advanced HIV infection have significantly declined. However, there are severe limits of HAART. Current anti-retroviral therapy do not allow viral eradication, therefore long-term use of the drugs is required. As a consequence, resistance develops in a significant portion of patients. Furthermore, several adverse metabolic side effects have been observed associated with the therapy. Therefore new approaches are required to control or eradicate this deadly virus infection.

Anti-HIV Agents↗
PubMed2005

[Outline of HIV replication and its cellular factors: the track of an invader in the cell].

A number of novel findings with reference to HIV replication have been reported even though it passed more than 20 years after a first HIV isolation. Although many cellular factors are known to be involved in the HIV replication, recently investigators discovered novel HIV-suppressive cellular factors such as APOBEC or TRIM5 alpha. Here, I describe and discuss how HIV uses the cellular machinery for its replication.

APOBEC-3G Deaminase↗
PubMed1995

A restriction enzyme map of the sex-linked late-feathering locus of chickens.

A 34-kb restriction endonuclease map of the region associated with an endogenous virus integration site and K, the gene that confers sex-linked late-feathering (LF) in chickens, is presented. Hybridizations of genomic blots of DNA from early-feathering and LF White Leghorns indicated that the region also contains additional repetitive elements upstream from a chicken repetitive (CR1) element. This extended map and the probes described should be useful in identifying the molecular alterations associated with this locus.

Alpharetrovirus↗
PubMedDate not supplied

FHIT as tumor suppressor: mechanisms and therapeutic opportunities.

Chromosomal abnormalities including homozygous deletions and loss of heterozygosity at 3p l4.2 are commonly observed in most human tumors, including lung, breast and kidney cancers. This region also contains the most common human fragile site FRA3B, a familial kidney cancer-associated translocation breakpoint and papilloma virus integration sites. The FHIT gene is a tumor suppressor, which is frequently inactivated by mentioned genomic alterations at 3pl4.2. In the last few years considerable amount of data describing inactivation of FHIT in a variety of human malignancies and demonstrating the tumor suppressor potential of Fhit has accumulated. However, these have not yet led to major advances in uncovering the precise molecular mechanism of Fhit action. This review focuses on the most recent progress in understanding of Fhit function as a tumor suppressor and opportunities for gene cancer therapy with Fhit.

Acid Anhydride Hydrolases↗