Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

HTLV-1-associated myelopathy/tropical spastic paraparesis (TSP/HAM) is a chronic CNS disease characterized by axomyelinic degeneration of the long axons of corticospinal tracts. Levels of NGF, NT-3, NT-4/5, BDNF, GDNF, CNTF, and FGF-2 were measured in the cerebrospinal fluid (CSF) of 21 TSP/HAM patients and 20 controls. NGF, BDNF, and FGF-2 levels were also determined in 19 patients with HIV motor cognitive motor syndrome, and in 21 subjects diagnosed with Creutzfeldt Jakob disease (CJD). No significant differences were detected in the concentrations of NGF, BDNF, NT-3, NT-4/5, GDNF, and CNTF in the CSF between TSP/HAM patients and controls. FGF-2 was significantly lower in the CSF of the three groups of patients compared with controls; the HIV group exhibited the lowest values. HIV patients differed from TSP/HAM in their significantly higher levels of NGF and lower levels of BDNF and FGF-2, whereas CJD patients differed only in their higher levels of NGF. Immunohistochemical studies were done of trophic factors (NGF and FGF-2) and neurotrophin receptors (trkA and p75) in spinal cord and motor cortical areas from anatomopathological cases of TSP/HAM. Results indicated that NGF is expressed in motoneurons and oligodendrocytes of the posterior column of the spinal cord. FGF-2 was detected in motoneurons and spinal cord vessels. p75 receptor was detected in cortical neurons. The absence of a significant change in the trophic factor levels in TSP/HAM may be attributed to a selective axonal lesion in a slow process.
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PMID:Trophic factors in cerebrospinal fluid and spinal cord of patients with tropical spastic paraparesis, HIV, and Creutzfeldt-Jakob disease. 1654 11

Lens epithelium-derived growth factor p75 (LEDGF/p75) is a DNA-binding, transcriptional co-activator that participates in HIV-1 integration site targeting. Using complementary approaches, we determined the mechanisms of LEDGF/p75 DNA-binding in vitro and chromatin-association in living cells. The binding of highly-purified, recombinant protein was assayed by surface plasmon resonance (SPR) and electrophoretic mobility gel shift. Neither assay revealed evidence for sequence-specific DNA-binding. Residues 146-197 spanning the nuclear localization signal (NLS) and two AT-hook motifs mediated non-specific DNA-binding, and DNA-binding deficient mutants retained the ability to efficiently stimulate HIV-1 integrase activity in vitro. Chromatin-association was assessed by visualizing the localization of EGFP fusion proteins in interphase and mitotic cells. Although a conserved N-terminal PWWP domain was not required for binding to condensed mitotic chromosomes, its deletion subtly affected the nucleoplasmic distribution of the protein during interphase. A dual AT-hook mutant associated normally with chromatin, yet when the mutations were combined with NLS changes or deletion of the PWWP domain, chromatin-binding function was lost. As the PWWP domain did not readily bind free DNA in vitro, our results indicate that chromatin-association is primarily affected through DNA-binding, with the PWWP domain likely contributing a protein interaction to the overall affinity of LEDGF/p75 for human chromatin.
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PMID:A tripartite DNA-binding element, comprised of the nuclear localization signal and two AT-hook motifs, mediates the association of LEDGF/p75 with chromatin in vivo. 1654 78

To replicate, a retrovirus must integrate a DNA copy of its RNA genome into a chromosome of the host cell. Integration is not random in the host genome but favors particular regions, and preferences differ among retroviruses. Several mechanisms might play a part in this favored integration targeting: (i) open chromatin might be preferentially accessible for viral DNA integration; (ii) DNA replication during cell division might facilitate access of integration complexes to favored sites; and (iii) cellular proteins bound to the host chromosome might tether integration complexes to favored regions. This review summarizes recent advances in understanding the mechanisms of retroviral integration, focusing on LEDGF/p75--the first cellular protein shown to have a role in directing HIV DNA integration. Studies on LEDGF/p75 indicate that it directs HIV integration site selection by a tethering interaction, whereas the chromatin accessibility or cell cycle models are less well supported. Understanding viral integration will help improve the safety of retrovirus-based vectors used in gene therapy.
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PMID:Retroviral DNA integration: HIV and the role of LEDGF/p75. 1673 94

Depletion of the transcriptional co-activator LEDGF/p75 by RNA interference alters the genome-wide pattern of HIV-1 integration, reducing integration into active genes, reducing integration into LEDGF/p75-regulated genes, and increasing integration into G+C-rich sequences. LEDGF/p75 is also able to act as a molecular tether linking HIV-1 integrase protein to chromatin, a phenomenon likely to underlie the integration site distribution effects. The LEDGF/p75 integrase-binding domain has been established but the domain or domains responsible for the chromatin-binding component of tethering are unknown. Here, we identify and characterize these domains. Complementary methods were used to assess condensed and uncondensed chromatin, and to determine the stringency of chromatin binding. Immuno-localization analyses revealed that an N-terminal PWWP domain and its beta-barrel substructure are needed for binding to metaphase chromatin. However, the PWWP domain is insufficient to transfer metaphase chromatin binding to green fluorescent protein, which requires addition of a downstream charged region (CR1). Biochemical analysis showed that full-length LEDGF/p75 resists Triton X-100 extraction from chromatin. To transfer Triton-resistant chromatin binding to green fluorescent protein, PWWP-CR1 is necessary but not sufficient. Further inclusion of a tandem pair of AT-hooks in combination with at least one of two identified downstream charged regions (CR2 or CR3) is needed. Deletion of just the PWWP or the AT-hook domain from full-length LEDGF/p75 reduced Triton-resistant chromatin binding, while deletion of both elements abolished it, underscoring their dominant and cooperative role. The results establish a molecular mechanism for LEDGF/p75-mediated tethering of HIV-1 integrase to chromatin.
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PMID:Identification and characterization of the chromatin-binding domains of the HIV-1 integrase interactor LEDGF/p75. 1679 62

LEDGF/p75 binding-defective IN mutant viruses were previously characterized as replication-defective, yet RNAi did not reveal an essential role for the host factor in HIV-1 replication. Correlative analyses of protein binding and viral fitness were expanded here by targeting 12 residues at the IN-LEDGF/p75 binding interface. Whereas many of the resultant viruses were defective, the majority of the INs displayed wild-type in vitro integration activities. Though an overall trend of parallel loss of LEDGF/p75 binding and HIV-1 infectivity was observed, a strict correlation was not. His-tagged IN(A128Q), derived from a phenotypically wild-type virus, failed to pull-down LEDGF/p75, but IN(A128Q) was effectively recovered in a reciprocal GST pull-down assay. Under these conditions, IN(H171A), also derived from a phenotypically wild-type virus, interacted less efficiently than a previously described interaction-defective mutant, IN(Q168A). Thus, the relative affinity of the in vitro IN-LEDGF/p75 interaction is not a universal predictor of IN mutant viral fitness.
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PMID:Structure-based mutagenesis of the integrase-LEDGF/p75 interface uncouples a strict correlation between in vitro protein binding and HIV-1 fitness. 1695 83

The mechanisms controlling retroviral integration have been the topic of intense interest, in part because of adverse clinical events that occurred during retrovirus-mediated human gene therapy. Here we investigate the use of artificial tethering interactions to constrain retroviral integration site selection in an in vitro model. During normal infection, HIV DNA integration is favored in active cellular transcription units. One component of the targeting mechanism is the cellular LEDGF/p75 protein. LEDGF/p75 binds tightly to HIV integrase (IN) protein, and depletion of LEDGF/p75 from target cells results in reduced integration in transcription units, suggesting integration targeting by a tethering mechanism. We constructed and analyzed fusions of LEDGF/p75 or its IN-binding domain (IBD) to the DNA-binding domain of phage lambda repressor protein (lambdaR). In the presence of the lambdaR-LEDGF/p75 fusions, increased strand transfer by IN was seen in target DNA near lambdaR-binding sites in vitro . These data support the idea that a direct interaction between LEDGF/p75 and IN can mediate targeting via a tethering mechanism, and provide proof of concept for the idea that protein-protein interactions might be engineered to constrain integration site selection during human gene therapy.
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PMID:Modulating target site selection during human immunodeficiency virus DNA integration in vitro with an engineered tethering factor. 1697 64

We initially identified lens epithelium-derived growth factor/p75 (LEDGF/p75) as a binding partner of human immunodeficiency virus type 1 (HIV-1) integrase. To investigate the role of LEDGF/p75 in HIV replication and its potential as a new antiviral target, we stably overexpressed two different fragments containing the integrase binding domain (IBD) of LEDGF/p75 fused to enhanced green fluorescent protein (eGFP). HIV-1 replication was severely inhibited by overexpression of the eGFP-IBD fusion proteins, while no inhibition was observed in cell lines overexpressing the interaction-deficient D366A mutant. Quantitative PCR pinpointed the block to the integration step, whereas nuclear import was not affected. Competition of the IBD fusion proteins with endogenous LEDGF/p75 for binding to integrase led to a potent defect in HIV-1 replication in both HeLaP4- and MT-4-derived cell lines. A previously described diketo acid-resistant HIV-1 strain remained fully susceptible to inhibition, suggesting that this strategy will also work in patients who harbor strains resistant to the current experimental integrase inhibitors. These data support LEDGF/p75 as an important cofactor for HIV replication and provide proof of concept for the LEDGF/p75-integrase interaction as a novel target for treating HIV-1 infection.
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PMID:Overexpression of the lens epithelium-derived growth factor/p75 integrase binding domain inhibits human immunodeficiency virus replication. 1698 86

Transcriptional co-activator LEDGF/p75 is the major cellular interactor of HIV-1 integrase (IN), critical to efficient viral replication. In this work, a series of INs from the Betaretrovirus, Gammaretrovirus, Deltaretrovirus, Spumavirus and Lentivirus retroviral genera were tested for interaction with the host factor. None of the non-lentiviral INs possessed detectable affinity for LEDGF in either pull-down or yeast two-hybrid assays. In contrast, all lentiviral INs examined, including those from bovine immunodeficiency virus (BIV), maedi-visna virus (MVV) and equine infectious anemia virus (EIAV) readily interacted with LEDGF. Mutation of Asp-366 to Asn in LEDGF ablated the interaction, suggesting a common mechanism of the host factor recognition by the INs. LEDGF potently stimulated strand transfer activity of divergent lentiviral INs in vitro. Unprecedentedly, in the presence of the host factor, EIAV IN almost exclusively catalyzed concerted integration, whereas HIV-1 IN promoted predominantly half-site integration, and BIV IN was equally active in both types of strand transfer. Concerted BIV and EIAV integration resulted in 5 bp duplications of the target DNA sequences. These results confirm that the interaction with LEDGF is conserved within and limited to Lentivirus and strongly argue that the host factor is intimately involved in the catalysis of lentiviral DNA integration.
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PMID:LEDGF/p75 interacts with divergent lentiviral integrases and modulates their enzymatic activity in vitro. 1715 50

An integrase dimer can process and integrate a single HIV-1 DNA end in vitro, whereas a tetramer is required to integrate two ends. LEDGF/p75 can potently stimulate integrase activity, but its effects on half- versus full-site integration have not been investigated. Stimulation of half-site but inhibition of full-site integration is revealed here. LEDGF/p75 seems to interfere with integrase oligomerization, but does not inhibit the catalytic activity of pre-assembled complexes. We therefore speculate that LEDGF/p75 function is restricted to a point in the viral lifecycle that occurs after the formation of the preintegration synaptic complex, for example, as a chromatin-associated tethering factor.
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PMID:LEDGF/p75 interferes with the formation of synaptic nucleoprotein complexes that catalyze full-site HIV-1 DNA integration in vitro: implications for the mechanism of viral cDNA integration. 1725 58

Retroviruses by definition insert their viral genome into the host cell chromosome. Although the key player of retroviral integration is viral integrase, a role for cellular cofactors has been proposed. Lentiviral integrases use the cellular protein LEDGF/p75 to tether the preintegration complex to the chromosome, although the existence of alternative host proteins substituting for the function of LEDGF/p75 in integration has been proposed. Truncation mutants of LEDGF/p75 lacking the chromosome attachment site strongly inhibit HIV replication by competition for the interaction with integrase. In an attempt to select HIV strains that can overcome the inhibition, we now have used T-cell lines that stably express a C-terminal fragment of LEDGF/p75. Despite resistance development, the affinity of integrase for LEDGF/p75 is reduced and replication kinetics in human primary T cells is impaired. Detection of the integrase mutations A128T and E170G at key positions in the LEDGF/p75-integrase interface provides in vivo evidence for previously reported crystallographic data. Moreover, the complementary inhibition by LEDGF/p75 knockdown and mutagenesis at the integrase-LEDGF/p75 interface points to the incapability of HIV to circumvent LEDGF/p75 function during proviral integration. Altogether, the data provide a striking example of the power of viral molecular evolution. The results underline the importance of the LEDGF/p75 HIV-1 interplay as target for innovative antiviral therapy. Moreover, the role of LEDGF/p75 in targeting integration will stimulate research on strategies to direct gene therapy vectors into safe landing sites.
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PMID:Virus evolution reveals an exclusive role for LEDGF/p75 in chromosomal tethering of HIV. 1739 62


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