Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An in vitro transcription system from mammary cells was established to study transcription of the long terminal repeat (LTR) of the mouse mammary tumor virus (MMTV). Experiments with progressive 5'-deletion constructs of the MMTV LTR revealed that a 19-base pair (bp) region from -41 to -23 bp, encompassing the TATA box and flanking DNA sequence, was as transcriptionally active as larger promoter constructs, both in nuclear extracts from human mammary cell lines (T47D and MCF7) and a nonmammary cell line (HeLa). The cell-free system was capable of supporting transcriptional induction by factors binding upstream of the TATA box, however, since purified glucocorticoid receptor-induced transcription in larger promoter constructs encompassing the MMTV hormone-responsive elements. Transcription from two other promoters, the adenovirus major late promoter and the human immunodeficiency virus LTR, also revealed a significant transcriptional contribution of upstream elements. The 19-bp TATA region from the MMTV LTR was shown to have considerably more activity in this transcription system than comparable TATA regions from other promoters. Sequences critical to the MMTV TATA region were evaluated by single base pair mutagenesis and found to comprise a consensus TATA box sequence, TATAAAA, as well as a single A just upstream of the TATAAAA sequence. Thus, the high level of basal transcription observed with the TATA region from MMTV is due to a perfect consensus TATA box sequence and a single base immediately 5' adjacent. It is likely that the high basal rate of transcription observed with this TATA box region on histone-free templates represents an inappropriate level of basal expression and that a complete evaluation of transactivation mechanisms in this system will require the recapitulation in vitro of the chromatin-mediated repressive state that exists in vivo.
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PMID:Role of the TATA box in transcription of the mouse mammary tumor virus long terminal repeat. 749 Nov 10

Dextrin-2-sulphate (D2S) is a sulphated polysaccharide which inhibits human immunodeficiency virus type 1 infection of T-cells by binding to the cell surface. During our investigations of the nature of this interaction, a cell membrane fraction was prepared by ultracentrifugation from the T-cell line, HPB-ALL. Separation of membrane proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis and analysis for binding proteins using ligand blotting showed that 3H-D2S bound, in a saturable and displaceable manner, to two regions corresponding to molecular weights of 14,000-18,000 and 28,000-32,000. The N-terminal sequences of two of the major protein components in the 14,000-18,000 region were consistent with those of histones H2B and H3. The presence of histone H2B in the cell membrane preparation was confirmed by immunoblotting and enzyme-linked immunosorbent assay using a specific antibody. Histone standards were used to determine the level of each histone in the cell membrane fraction. In addition, the binding of 3H-D2S to purified histone standards was quantified. These results show that all of the binding of 3H-D2S to proteins in the 14,000-18,000 region of the cell membrane preparation can be attributed to the histones present. In contrast to HPB-ALL cells, a cell membrane fraction from freshly isolated human peripheral blood lymphocytes contained very low levels of histones. However, after culture with phytohaemagglutinin for 3 days the cell membrane fraction contained greatly increased levels of histones. To exclude the possibility of contamination of the cell membrane preparation with histones derived from the nucleus, cell membranes were also prepared using an affinity-based method using polyethyleneimine-cellulose. Immunoblotting of adsorbed plasma membranes showed the presence of histone H2B. SDS-polyacrylamide gels stained for protein also indicated that the preparation contained histones H1, H2A, H3 and H4. In further experiments whole cells were used to avoid contamination from nuclear proteins. Lactoperoxidase mediated 125I labelling, a method specific for radiolabelling cell surface proteins, confirmed the presence of histones H2B, H3 and H4 on the surface of HPB-ALL cells. Also, incubation of HPB-ALL cells or phytohaemagglutinin-activated peripheral blood lymphocytes with D2S caused displacement of histones from the cell surface into the supernatant without altering cell viability. In addition, immunocytochemistry of freshly isolated peripheral blood lymphocytes showed that histone H2B was located predominantly in the nucleus. However, in phytohaemagglutinin-activated peripheral blood lymphocytes immunoreactive material was also prominent in the endoplasmic reticulum and on the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Extra-nuclear location of histones in activated human peripheral blood lymphocytes and cultured T-cells. 764 32

This report describes the inhibition of protein kinase C (PKC) by a synthetic peptide corresponding to a viral sequence expressed in mammalian cells. The peptide corresponds to cytoplasmic domain residues 828-848 of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (gp41), and it inhibits Ca(2+)- and phosphatidylserine (PS)-dependent phosphorylation of synthetic peptide substrates and histone by purified PKC with IC50 values ranging from 9 to 32 microM. Although previously described pKC-inhibitory synthetic peptides corresponding to sequences expressed in mammalian cells are also effective against the phosphorylation of synthetic peptide substrates, they fail to affect PKC-catalysed phosphorylation of potent protein substrates such as histone. This may limit their usefulness as inhibitors of PKC-catalysed protein phosphorylation in cellular systems. PKC activation is a major contributing factor in multidrug resistance (MDR) in cancer. Our observation that the synthetic peptide gp41(828-848) inhibits pKC-catalysed phosphorylation of a protein substrate suggests the potential value of expressing the viral sequence gp41(828-848) in cancer cells as a novel in vitro model system of MDR reversal.
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PMID:Inhibition of protein kinase C by a synthetic peptide corresponding to cytoplasmic domain residues 828-848 of the human immunodeficiency virus type 1 envelope glycoprotein. 785 Jul 71

DNA copies of the human immunodeficiency virus (HIV) genome integrate nonrandomly into the chromosomal DNA of the host cell. In this report, we investigate the molecular basis of this selectivity using the virus-encoded HIV integrase to direct integration of a synthetic HIV long terminal repeat substrate into either DNA molecules of known structure or previously defined nucleosomal complexes. We find that the structure of the target greatly influences the site of integration, and, moreover, DNA curvature, flexibility, and rigidity in solution all influence the frequency of integration. Importantly, for DNA with all of these properties, the distortion of the double helix directed by association with the histone proteins promotes the integration reaction and alters the distribution of sites that are selected for integration. We suggest that both intrinsic DNA structure and the folding of DNA into chromosomal structures will exert a major influence on target site selection for integration of the viral genome.
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PMID:The influence of DNA and nucleosome structure on integration events directed by HIV integrase. 792 89

We have examined the consequences of DNA distortion and specific histone-DNA contacts within the nucleosome for integration mediated by the human immunodeficiency virus (HIV)-encoded integrase enzyme. We find that sites of high-frequency integration cluster in the most severely deformed, kinked DNA regions within the nucleosome core. This may reflect either a preference for a wide major groove for association of the integrase or a requirement for target DNA distortion in the DNA strand transfer mechanism. Both the distortion and folding of the target DNA through packaging into nucleosomes may influence the selection of HIV integration sites within the chromosome.
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PMID:Human immunodeficiency virus integrase directs integration to sites of severe DNA distortion within the nucleosome core. 801 88

Here we report the presence of a protein kinase activity associated with human immunodeficiency virus type 1 (HIV-1) particles. We observed phosphorylation of five major proteins by the endogenous protein kinase activity. Phosphoamino acid analysis revealed phosphorylated serine and threonine residues. In addition, we observed autophosphorylation of two proteins in the presence of gamma-ATP in an in-gel phosphorylation assay. These two proteins are not linked by a disulfide bond, suggesting that two different protein kinases are associated with HIV-1 virions. Our results indicate the presence of ERK2 mitogen-activated protein kinase and of a 53,000-molecular-weight protein kinase associated with virions. Moreover, the use of different HIV strains derived from T cells and promonocytic cells, as well as the use of human T-cell leukemia virus type 1 particles, demonstrates that ERK2 is strongly associated with retrovirus particles in a cell-independent manner. Exogenous substrates, such as histone proteins, and a viral substrate, such as Gag protein, are phosphorylated by virus-associated protein kinases.
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PMID:Association of ERK2 mitogen-activated protein kinase with human immunodeficiency virus particles. 915 81

To investigate mechanisms yielding DNase I-hypersensitive sites (DHSs) at gene regulatory regions, we have initiated a biochemical analysis of transcription factor binding and nucleosome remodeling with a region of the human immunodeficiency virus 1 (HIV-1) 5' long terminal repeat (LTR) that harbors constitutive DHSs in vivo. In vitro reconstitution of an HIV-1 5' LTR fragment into nucleosome core particles demonstrates that Sp1, NF-kappaB1, LEF-1, ETS-1 and USF can gain access to their binding sites in HIV-1 nucleosomal DNA. The factor-bound mononucleosomes resist histone displacement from the DNA by the chromatin remodeling activity, SW1-SNF, or the histone chaperone, nucleoplasmin, suggesting that the binding of these factors to nucleosomal HIV-1 sequences forms a stable complex that includes the underlying histones. However, when the HIV-1 5' LTR fragment is incorporated into a nucleosomal array, Sp1 and NF-kappaB1 binding produce regions of enhanced DNase I sensitivity specifically at the HIV-1 nucleosome. These regions resemble the observed in vivo DHSs, yet the HIV-1 nucleosome remains intact even in the presence of nucleoplasmin. Thus, the constitutive DHSs identified at the HIV-1 enhancer in native chromatin may reflect the presence of a ternary complex composed of transcriptional activators, histones and DNA.
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PMID:Stable co-occupancy of transcription factors and histones at the HIV-1 enhancer. 917 59

A unique aspect of the retrovirus life cycle is the obligatory integration of the provirus into host cell chromosomes. Unlike viruses that do not integrate, retroviruses must conserve an ability to activate transcription from a chromatin context. Human immunodeficiency virus (HIV)-1 encodes an unusual and an unusually potent transcriptional transactivator, Tat, which binds to a nascent viral leader RNA, TAR. The action of Tat has been well studied in various reductive model systems; however, the physiological mechanism through which Tat gains access to chromatin-associated proviral long terminal repeats (LTRs) is not understood. We show here that a nuclear histone acetyltransferase activity associates with Tat. Intracellularly, we found that Tat forms a ternary complex with p300 and P/CAF, two histone acetyltransferases (HATs). A murine cell defect in Tat transactivation of the HIV-1 LTR was linked to the reduced abundance of p300 and P/CAF. Thus, overexpression of p300 and P/CAF reconstituted Tat transactivation of the HIV-1 LTR in NIH3T3 cells to a level similar to that observed for human cells. By using transdominant p300 or P/CAF mutants that lack enzymatic activity, we delineated a requirement for the HAT component from the latter but not the former in Tat function. Finally, we observed that Tat-associated HAT is preferentially important for transactivation of integrated, but not unintegrated, HIV-1 LTR.
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PMID:Activation of integrated provirus requires histone acetyltransferase. p300 and P/CAF are coactivators for HIV-1 Tat. 973 96

The human immunodeficiency virus (HIV) trans- activator protein, Tat, stimulates transcription from the viral long-terminal repeats (LTR) through an RNA hairpin element, trans-activation responsive region (TAR). We and others have shown that trans-activator protein (Tat)-associated histone acetyltransferases (TAHs), p300 and p300/CBP-associating factor (PCAF), assist functionally in the activation of chromosomally integrated HIV-1 LTR. Here, we show that p300 and PCAF also directly acetylate Tat. We defined two sites of acetylation located in different functional domains of Tat. p300 acetylated Lys50 in the TAR RNA binding domain, while PCAF acetylated Lys28 in the activation domain of Tat. In support of a functional role for acetylation in vivo, histone deacetylase inhibitor (trichostatin A) synergized with Tat in transcriptional activation of the HIV-1 LTR. Synergism was TAR-dependent and required the intact presence of both Lys28 and Lys50. Mechanistically, acetylation at Lys28 by PCAF enhanced Tat binding to the Tat-associated kinase, CDK9/P-TEFb, while acetylation by p300 at Lys50 of Tat promoted the dissociation of Tat from TAR RNA that occurs during early transcription elongation. These data suggest that acetylation of Tat regulates two discrete and functionally critical steps in transcription, binding to an RNAP II CTD-kinase and release of Tat from TAR RNA.
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PMID:HIV-1 tat transcriptional activity is regulated by acetylation. 1054 21

Upon infection of susceptible cells, the RNA genome of the human immunodeficiency virus type 1 (HIV-1) is reverse transcribed into double-stranded DNA, which can be subsequently integrated into the cellular genome. After integration, the viral long terminal repeat (LTR) promoter is present in a nucleosome-bound conformation and is transcriptionally silent in the absence of stimulation. Activation of HIV-1 gene expression is concomitant with an acetylation-dependent rearrangement of the nucleosome positioned at the viral transcription start site. Thus, similar to most cellular genes, the transcriptional state of the integrated HIV-1 provirus is closely linked to histone acetylation. This enzymatic activity results from the function of histone-specific nuclear acetyltransferase (HAT) enzymes. Efficient viral transcription is strongly dependent on the virally-encoded Tat protein. the mechanism by which Tat increases the rate of transcriptional initiation has been recently demonstrated and involves the interaction of Tat with the transcriptional coactivator p300 and the closely related CREB-binding protein (CBP), having histone acetyltransferase activity.
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PMID:Chromatin control of HIV-1 gene expression. 1071 Jul 18


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