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)

The viral transactivator proteins Rex and Rev are necessary for the expression of structural proteins of human T-cell leukemia virus type I and human immunodeficiency virus type 1, respectively. Although the interaction of Rex/Rev with a cellular cofactor(s) has been thought to be required for Rex/Rev action, there is no suitable system to search for the cofactor(s) in mammalian cells. We found that a Rex mutant, TAgRex, which contains a simian virus 40 nuclear localization signal in place of the N-terminal 19 amino acids of Rex, could dominantly inhibit wild-type Rex/Rev functions. The inhibition did not require either Rev response element/Rex response element binding or the oligomerization ability of the mutant, but it did require a region around amino acid 90 of the Rex protein, suggesting that TAgRex sequestered the cellular cofactor. Complementation with the eukaryotic translation initiation factor 5A (eIF-5A) in this system could restore the impaired Rex function. These results indicate that eIF-5A is the cofactor indispensable for Rex function. Additionally, by using a two-hybrid system, the homo-oligomer formation of Rex was found to be mediated by the region around amino acid 90 in addition to Tyr-64 and Trp-65 of Rex protein. Thus, eIF-5A may play a part in the formation of the Rex homo-oligomer.
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PMID:Effects of translation initiation factor eIF-5A on the functioning of human T-cell leukemia virus type I Rex and human immunodeficiency virus Rev inhibited trans dominantly by a Rex mutant deficient in RNA binding. 770 41

Protein synthesis initiation factor 5A (eIF-5A) from human erythrocytes was found to be a substrate for both plasma transglutaminase (Factor XIIIa) and guinea pig liver transglutaminase (GPLTG). When purified eIF-5A was incubated with GPLTG or Factor XIIIa in the presence of succinylated beta-casein, a covalent complex was identified. By isolating and analysing the product of the transglutaminases (TGases) reaction, the site of modification on eIF-5A has been identified as the unique amino acid hypusine. The complex beta-casein.eIF-5A was enzymatically digested with proteinases and the predicted covalent cross-link of gamma-glutamyl-omega-hypusine was isolated from the digests by ion-exchange chromatography and purified by reversed-phase h.p.l.c. Acid hydrolysis of the purified dipeptide yielded equimolar amounts of hypusine and glutamic acid. Furthermore, fast atom bombardment m.s. analysis confirmed the isomer assignment to be gamma-glutamyl-omega-hypusine. These data indicate that hypusine-50 of the eIF-5A chain functions as acyl acceptor substrate for TGases, and reveal that eIF-5A may be cross-linked to intracellular proteins by TGases. Because the precise function of eIF-5A is still unknown, our results appear particularly stimulating in the light of the recent finding of a new biological role for this protein as a cellular factor binding specifically to the human immunodeficiency virus-1 Rev activation domain [Ruhl, Himmelspach, Bahr, Hammerschmid, Jaksche, Wolff, Auschauer, Farrington, Probst, Bevec and Hauber (1993) J. Cell Biol. 123, 1309-1320].
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PMID:Identification of a substrate site for transglutaminases on the human protein synthesis initiation factor 5A. 784 70

In the absence of Rev or the Rev-responsive element, the Rev-dependent human immunodeficiency virus type 1 (HIV-1) RNAs do not behave as mRNAs; rather, they exhibit nuclear defects in splicing and/or nuclear export and cytoplasmic defects in stability and translation. A translational initiation factor, eIF-5A, has recently been shown to bind specifically to the Rev activation domain. As the binding of poly(A)-binding protein 1 (PAB1) to the poly(A) tail of mRNAs is involved in both the stability and translation of cytoplasmic mRNAs, we investigated whether Rev might influence the association of PAB1 with cytoplasmic HIV-1 RNAs. Antibodies were generated against PAB1. We used these antibodies in an immunoprecipitation assay to detect specific binding of PAB1 to cytoplasmic mRNAs. We found that in the presence of Rev, PAB1 was associated with Rev-dependent and Rev-independent RNAs in the cytoplasm of transfected cells. However, in the absence of functional Rev, we found little or no PAB1 associated with Rev-dependent RNAs. These RNAs were capable of binding PAB1 in vitro. These results demonstrate that HIV-1 RNAs are defective in PAB1 association in the absence of Rev.
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PMID:Human immunodeficiency virus type 1 Rev is required in vivo for binding of poly(A)-binding protein to Rev-dependent RNAs. 805 25

Eukaryotic initiation factor 5A(eIF-5A) is a cellular cofactor require d for the function of the human immunodeficiency virus type-1 (HIV-1) Rev trans-activator protein. The majority of a set of eIF-5A mutants did not support growth of yeast cells having an inactivated genomic copy of eIF-5A, indicating that the introduced mutation eliminated eIF-5A activity. Two nonfunctional mutants, eIF-5AM13 and eIF-5AM14, retained their binding capacity for the HIV-1 Rev response element:Rev complex. Both mutants were constitutively expressed in human T cells. When these T cells were infected with replication-competent HIV-1, virus replication was inhibited. The eIF-5AM13 and eIF5AM14 proteins blocked Rev trans-activation and Rev-mediated nuclear export.
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PMID:Inhibition of HIV-1 replication in lymphocytes by mutants of the Rev cofactor eIF-5A. 859 53

To gain insight into the role of the eukaryotic translation initiation factor, eIF-5A, we investigated the subcellular distribution of this protein in several cultured cell types and at different stages of the cell cycle using a highly potent monospecific polyclonal antibody to eIF-5A. Studies using indirect immunofluorescence and confocal microscopy in conjunction with subcellular fractionation demonstrate that eIF-5A is primarily localized in the cytoplasm of cells. This cytoplasmic location of eIF-5A is not significantly altered in different stages of the cell cycle and the subcellular distribution pattern of eIF-5A is not changed by viral oncogene transformation. Cell fractionation experiments identified two populations of eIF-5A in the cytoplasm, a soluble fraction and a fraction bound to internal membranes. By double immunofluorescence staining with an antibody against calnexin, a resident protein of the endoplasmic reticulum (ER), we demonstrate that the membrane-bound fraction of eIF-5A colocalizes with the ER and not with the cytoskeleton. Expression of Rev, a regulatory protein of human immunodeficiency virus type 1 (HIV-1), does not alter the subcellular distribution of endogenous eIF-5A in these cells. eIF-5A is detected in all tissues and cells examined including extracts prepared from Xenopus oocytes. Our results indicate that eIF-5A is a ubiquitous cytoplasmic protein and suggest that a site of eIF-5A function is likely to be in association with the ER.
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PMID:The subcellular distribution of eukaryotic translation initiation factor, eIF-5A, in cultured cells. 866 Sep 23

Previously, we described two mutants of the cellular Rev co-factor, eukaryotic initiation factor 5A (eIF-5A M13 and M14), which suppress human immunodeficiency virus type 1 (HIV-1) SF2 replication in clonal T cell lines. This study introduced the notion that it is possible to develop gene therapies against infectious agents on the basis of mutant host factors required for viral replication. In this report, we provide further evidence to support this new paradigm and describe murine leukemia virus (MLV)-based retroviral vectors expressing three different eIF-5A mutants from the viral long terminal repeat (LTR). HIV-1 replication (SF2, HXB-3) was reduced up to 2 orders of magnitude in transduced, polyclonal T cell populations. All eIF-5A mutants also showed antiviral activity (approximately seven-fold reduction) in a chronic HIV-1 infection model. Expression of eIF-5A mutant M13 delta in peripheral blood lymphocytes (PBLs) showed no difference in proliferation and metabolic activity as determined in a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT)-assay, suggesting that expression of this type of mutant protein is not associated with cellular toxicity. In summary, these data suggest that gene therapy for HIV-1 infection can be developed on the basis of mutants of the Rev co-factor eIF-5A.
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PMID:Intracellular expression of cellular eIF-5A mutants inhibits HIV-1 replication in human T cells: a feasibility study. 889 78

The subcellular distributions of the endogenous eukaryotic translation initiation factor, eIF-5A, and Rev, a protein of the human immunodeficiency virus proposed to interact with eIF-5A, were studied in COS-7 cells treated with inhibitors of RNA or protein synthesis. We have previously shown that transiently expressed Rev is localized in the nucleolus, whereas eIF-5A is primarily in the cytoplasm. The subcellular localization of Rev was not affected by treatment with protein synthesis inhibitors (cycloheximide, CHX, 10 micrograms/ml; puromycin, 10 micrograms/ml), although its location changed from predominantly the nucleolus to the cytoplasm after treatment with RNA synthesis inhibitors (actinomycin D, 4 micrograms/ml, and 5,6-dichloro-1 beta-D-ribofuranosylbenzimidazole, DRB; 0.1 mM), as previously reported. In contrast, none of the RNA synthesis inhibitors (alpha-amanitin, 10 micrograms/ml; actinomycin D, 4 micrograms/ml, and DRB, 0.1 mM) caused any significant changes in the subcellular distribution pattern of eIF-5A. However, treatment with puromycin, a protein synthesis inhibitor known to dissociate ribosomes, dramatically altered the subcellular distribution pattern of eIF-5A in 30% of the cell population. In these cells, the staining of eIF-5A was changed from an endoplasmic reticulum (ER) net work-like perinuclear structure to a patched dotted pattern dispersed throughout the cytoplasm. This change was not observed in the same cells stained for calnexin, an ER resident protein, nor in cells treated with CHX, which freezes the ribosomes to block protein synthesis. Our data suggest that eIF-5A does not shuttle between the nucleus and cytoplasm in the same way as Rev. Our findings are consistent with our previous conclusion that eIF-5A is associated with the ER through ribosomes and support a role for eIF-5A in protein synthesis.
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PMID:Effects of inhibitors of RNA and protein synthesis on the subcellular distribution of the eukaryotic translation initiation factor, eIF-5A, and the HIV-1 Rev protein. 928 97

The human immunodeficiency virus type 1 (HIV-1) Rev protein binds to unspliced HIV-1 pre-mRNA and exports it from the nucleus. Rev itself can "shuttle" between the nucleus and cytoplasm. This bi-directional transport is mediated by two specific Rev sequences: a nuclear localisation signal (NLS), which overlaps the RNA-binding domain, and a distinct nuclear export signal (NES). In this study we characterised new monoclonal antibodies that bind different epitopes of Rev, including the import and export sequences. In RNA bandshift assays, we observed that formation of a multimeric complex between Rev and its target RNA completely masks the Rev NLS, whereas the NES remains readily accessible. We then tested for signal-mediated interactions between Rev and different nuclear transport receptors, using mutations in the Rev NES or NLS to control for specificity. Extensive biochemical analyses did not reveal any direct NES-dependent interaction between Rev (free or RNA-bound) and the previously proposed export co-factors, human RIP/Rab and eIF-5A. By contrast, similar tests showed that Rev binds directly via its arginine-rich NLS to the human nuclear import receptor, importin-beta. This interaction was highly specific and was abolished by mutation in the Rev NLS. Importin-beta did not bind to the RNA-bound form of Rev, providing a mechanism to ensure that Rev is imported only following release of its RNA cargo. Unlike many NLS-containing proteins that bind stably to an importin-alpha/beta heterodimer, the binding of Rev to importin-beta was actually blocked by importin-alpha receptor. Our findings suggest that Rev and importin-alpha bind (via an arginine-rich sequence) to a similar region on importin-beta. In addition, we show that the complex between Rev and importin-beta can be dissociated by the nuclear Ran GTPase, but only when Ran is in the GTP-bound form. The series of interactions we describe provide a novel pathway for the import of Rev across the nuclear pore complex, and a mechanism for its release into the nucleoplasm.
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PMID:Interactions between HIV Rev and nuclear import and export factors: the Rev nuclear localisation signal mediates specific binding to human importin-beta. 940 52

Proper function of the Rev regulatory system is essential for the replication of lentiviruses, including feline immunodeficiency virus (FIV) and human immunodeficiency virus type 1 (HIV-1). Specifically, Rev affects the overall stability of viral mRNAs that encode necessary structural and enzymatic proteins. In turn, the eukaryotic initiation factor (eIF-5A) is indispensable for Rev function and is the only known protein whose biologically active form requires the unique amino acid, hypusine. Because 1,8-diaminooctane blocks the formation of hypusine by disrupting the cellular enzyme, deoxyhypusine synthase, thereby preventing activation of eIF-5A, we investigated the effects of 1,8-diaminooctane on posttranscriptional regulation. These are the first results to demonstrate that diaminooctane significantly reduced viral replication in a dose-dependent manner, even under conditions of contact inhibition, diminishing the compound's effect on cell proliferation. Similarly, the addition of increased concentrations of diaminooctane caused a reduction in the expression of a Rev-dependent CAT system without affecting a Rev-independent CAT system. At the RNA level, exposure of chronically infected CrFK cells to increasing concentrations of diaminooctane substantially decreased the levels of unspliced and singly spliced viral mRNAs and increased the relative amounts of multiply spliced transcripts in the cytoplasm. The findings of this study are the first demonstration that FIV, similar to HIV-1, requires eIF-5A for efficient Rev function and that small molecule intervention can indirectly target this lentivirus regulatory system.
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PMID:Effects of 1,8-diaminooctane on the FIV Rev regulatory system. 1249 Apr 7