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)

A cDNA encoding a double-stranded-RNA (dsRNA)-binding protein was isolated by screening a HeLa cell cDNA expression library for proteins that bind the HIV-1 Rev-responsive-element RNA. The cDNA encoded a protein that was identical to TRBP, the previously reported cellular protein that binds the transactivation response element (TAR) RNA of human immunodeficiency virus type 1. TRBP inhibited phosphorylation of the interferon-induced ribosome-associated protein kinase PKR and of the eukaryotic translation initiation factor eIF-2 alpha in a transient-expression system in which the translation of a reporter gene was inhibited by the localized activation of PKR. TRBP expression in HeLa cells complemented the growth and protein-synthesis defect of a vaccinia virus mutant lacking the expression of the dsRNA-binding protein E3L. These results implicate TRBP as a cellular regulatory protein that binds RNAs containing specific secondary structure(s) to mediate the inhibition of PKR activation and stimulate translation in a localized manner.
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PMID:TAR RNA-binding protein is an inhibitor of the interferon-induced protein kinase PKR. 751 77

The yeast two-hybrid system and far-Western protein blot analysis were used to demonstrate dimerization of human double-stranded RNA (dsRNA)-dependent protein kinase (PKR) in vivo and in vitro. A catalytically inactive mutant of PKR with a single amino acid substitution (K296R) was found to dimerize in vivo, and a mutant with a deletion of the catalytic domain of PKR retained the ability to dimerize. In contrast, deletion of the two dsRNA-binding motifs in the N-terminal regulatory domain of PKR abolished dimerization. In vitro dimerization of the dsRNA-binding domain required the presence of dsRNA. These results suggest that the binding of dsRNA by PKR is necessary for dimerization. The mammalian dsRNA-binding protein TRBP, originally identified on the basis of its ability to bind the transactivation region (TAR) of human immunodeficiency virus RNA, also dimerized with itself and with PKR in the yeast assay. Taken together, these results suggest that complexes consisting of different combinations of dsRNA-binding proteins may exist in vivo. Such complexes could mediate differential effects on gene expression and control of cell growth.
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PMID:Double-stranded-RNA-dependent protein kinase and TAR RNA-binding protein form homo- and heterodimers in vivo. 756 51

TRBP is a human cellular protein that binds the human immunodeficiency virus type 1 TAR RNA. Here, we show that the intact presence of amino acids 247 to 267 in TRBP correlates with its ability to bind RNA. This region contains a lysine- and arginine-rich motif, KKLAKRNAAAKMLLRVHTVPLDAR. A 24-amino-acid synthetic peptide (TR1) of this sequence bound TAR RNA with affinities similar to that of the entire TRBP, thus suggesting that this short motif contains a sufficient RNA-binding activity. Using RNA probe-shift analysis, we determined that TR1 does not bind all double-stranded RNAs but prefers TAR and other double-stranded RNAs with G+C-rich characteristics. Immunoprecipitation of TRBP from human immunodeficiency virus type 1-infected T lymphocytes recovered TAR RNA. This is consistent with a TRBP-TAR ribonucleoprotein during viral infection. Computer alignment revealed that TR1 is highly homologous to the RNA-binding domain of human P1/dsI protein kinase and two regions within Drosophila Staufen. We suggest that these proteins are related by virtue of sharing a common RNA-binding moiety.
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PMID:Relatedness of an RNA-binding motif in human immunodeficiency virus type 1 TAR RNA-binding protein TRBP to human P1/dsI kinase and Drosophila staufen. 845 7

The human T-cell leukemia virus type 1 (HTLV-1)-encoded Tax protein activates transcription from the long terminal repetition via association with host cellular factors. In this study, we searched for cellular proteins that interact with Tax and modulate its activity by using the yeast two-hybrid system. One of the strongest interactors was found to be identical with TRBP, which was previously shown to bind to the RNA encoded by the Tat response element of human immunodeficiency virus type 1. Interactions are demonstrated with Escherichia coli-expressed proteins in vitro and in mammalian cells, using one- and two-hybrid systems, and with antibodies that coprecipitate Tax and TRBP at physiological TRBP concentrations. Moreover, TRBP, when directed into the cytoplasm, is capable of preventing transport of Tax into the nucleus. A 60-amino-acid polypeptide suffices for binding to Tax. TRBP inhibits activation of transcription by both Tax and GAL4-Tax fusion proteins. Inhibition is specific for Tax and is not seen with the other activators tested. Our data are consistent with the interpretation that TRBP inhibits the interplay of Tax with the transcription machinery or accessory factors.
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PMID:Specific repression of Tax trans-activation by TAR RNA-binding protein TRBP. 906 Jun 15

We have previously found the sequence having potential for encoding a new protein in the human leukocyte antigen (HLA) class II region. The predicted amino acid sequence showed a significant sequence homology to the Xenopus double-stranded RNA-binding protein (Xlrbp) and the human cellular protein bound to the transactivation response (TAR) of human immunodeficiency virus type-1 (HIV-1) RNA (TRBP). Reverse transcription-polymerase chain reaction (RT-PCR) with poly(A)(+) RNA prepared from human peripheral lymphocytes and direct sequencing analyses in this study showed that the transcripts of the gene encoding the putative RNA-binding protein occurred in human cells: the gene was provisionally named Homo sapiens RNA-binding protein (hsRBP). From the result of Southern blot analyses, it appears that multiple copies of hsRBP are present in the human genome. Together with the known cDNAs having a high sequence homology to hsRBP, the data presented here suggest that the multigene family of the double-stranded RNA-binding protein exists in the human genome.
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PMID:Molecular analyses of the possible RNA-binding protein gene located in the human leukocyte antigen (HLA)--DR subregion. 1056 19

Trans-activation response (TAR) RNA-binding protein (TRBP) is a cellular protein that binds to the human immunodeficiency virus-1 (HIV-1) TAR element RNA. It has two double-stranded RNA binding domains (dsRBDs), but only one is functional for TAR binding. TRBP interacts with the interferon-induced protein kinase R (PKR) and inhibits its activity. We used the yeast two-hybrid assay to map the interaction sites between the two proteins. We show that TRBP and PKR-N (178 first amino acids of PKR) interact with PKR wild type and inhibit the PKR-induced yeast growth defect in this assay. We characterized two independent PKR-binding sites in TRBP. These sites are located in each dsRBD in TRBP, indicating that PKR-TRBP interaction does not require the RNA binding activity present only in dsRBD2. TRBP and its fragments that interact with PKR reverse the PKR-induced suppression of HIV-1 long terminal repeat expression. In addition, TRBP activates the HIV-1 long terminal repeat expression to a larger extent than the addition of each domain. These data suggest that TRBP activates gene expression in PKR-dependent and PKR-independent manners.
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PMID:Two dimerization domains in the trans-activation response RNA-binding protein (TRBP) individually reverse the protein kinase R inhibition of HIV-1 long terminal repeat expression. 1143 32

TRBP1 and TRBP2 are isoforms of a double-stranded RNA-binding protein that differ in their N-terminal end and were each identified by binding to human immunodeficiency virus type 1 (HIV-1) trans-activation-responsive RNA. TRBP1 and TRBP2 also bind and modulate the function of the double-stranded RNA-activated protein kinase, protein kinase R. Both proteins increase long terminal repeat expression in human and murine cells, and their gene has been mapped to human chromosome 12. We have isolated and characterized the complete tarbp2 gene (5493 bp) coding for the two TRBP proteins. Two adjacent promoters initiate transcription of alternative first exons for TRBP1 and TRBP2 mRNAs that are spliced onto common downstream exons. TRBP2 transcription and translation start sites are localized within the first intron of TRBP1. TRBP promoters are TATA-less but have CCAAT boxes, a CpG island, and several potential binding sites for transcriptional factors. Promoter deletion analysis identified two regions from position -1397 to -330 for TRBP1 and from position -330 to +38 for TRBP2 that are important for promoter function. TRBP2 promoter activity was expressed at a higher level compared with TRBP1 promoter. In addition, a specific down-regulation of TRBP1 and TRBP2 promoter activity was identified in human astrocytic cell line U251MG compared with HeLa cells. This minimal TRBP promoter activity may account for minimal HIV-1 replication in astrocytes.
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PMID:Organization of the human tarbp2 gene reveals two promoters that are repressed in an astrocytic cell line. 1164 96

A sensitive reporter assay to measure human immunodeficiency virus type 1 (HIV-1) protease (PR) activity is described in this manuscript. This assay measures PR activity as a function of the resonance energy transfer (RET) between a donor molecule [humanized sea pansy Renilla reniformis luciferase (hRLuc)] and an energy acceptor molecule, humanized green fluorescent protein (hGFP2) when expressed in mammalian cells. This is a naturally occurring phenomenon and is an emerging and powerful technology that has significant advantages over alternative in vitro PR assays. The HIV-1 Gag-p2/Gag-p7 (p2/p7) PR site was inserted between hGFP2 and hRLuc. The newly created vector, hRLuc-p2/p7-hGFP2 was co-expressed with an HIV-1 codon-optimized PR+ or PR- Gag/Pol expressor. Expression of the hRLuc-p2/p7-hGFP2 alone or with the PR- Gag-Pol expressor generated a BRET2 indicating that the PR cleavage site was not cleaved, whereas the inclusion of the PR+ Gag-Pol produced a significant reduction in the BRET2. The inclusion of PR inhibitors Saquinavir or Amprenavir, or the expression of a p2/p7 PR substrate mutant also blocked the cleavage to result in a stable BRET2 signal. Because the HIV-1 auxiliary protein Vif has been shown to modulate the HIV-1p2/p7 cleavage, this assay was then validated in studies in which Vif was expressed. When Vif was overexpressed along with hRLuc-p2/p7-hGFP2 and PR+ Gag-Pol, the decrease in BRET2 was abrogated in a dose-dependent manner, demonstrating that supraphysiologic levels of Vif block p2/p7 cleavage. An accumulation of a Gag processing intermediate was observed, indicating that p2/p7 cleavage was negatively affected. Overexpression of an RNA-binding-defective Staufen protein or a related dsRNA-binding protein TRBP had no effect on PR cleavage activity as shown by Western and BRET2 analyses. The p2/p7 processing data were confirmed by Western blot analyses. BRET is non-invasive and occurs within live cells, is measured in real time, and is not restricted to cellular compartments making it an especially attractive technology to identify small bioactive inhibitory molecules. This PR BRET2 biosensor assay can be adapted for high throughput screening of new HIV-1 PR inhibitors. It can be employed to screen for antiviral compounds that also target the proteases of other viruses.
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PMID:A human immunodeficiency virus type 1 protease biosensor assay using bioluminescence resonance energy transfer. 1595 Oct 29

MicroRNAs (miRNAs) are generated by a two-step processing pathway to yield RNA molecules of approximately 22 nucleotides that negatively regulate target gene expression at the post-transcriptional level. Primary miRNAs are processed to precursor miRNAs (pre-miRNAs) by the Microprocessor complex. These pre-miRNAs are cleaved by the RNase III Dicer to generate mature miRNAs that direct the RNA-induced silencing complex (RISC) to messenger RNAs with complementary sequence. Here we show that TRBP (the human immunodeficiency virus transactivating response RNA-binding protein), which contains three double-stranded, RNA-binding domains, is an integral component of a Dicer-containing complex. Biochemical analysis of TRBP-containing complexes revealed the association of Dicer-TRBP with Argonaute 2 (Ago2), the catalytic engine of RISC. The physical association of Dicer-TRBP and Ago2 was confirmed after the isolation of the ternary complex using Flag-tagged Ago2 cell lines. In vitro reconstitution assays demonstrated that TRBP is required for the recruitment of Ago2 to the small interfering RNA (siRNA) bound by Dicer. Knockdown of TRBP results in destabilization of Dicer and a consequent loss of miRNA biogenesis. Finally, depletion of the Dicer-TRBP complex via exogenously introduced siRNAs diminished RISC-mediated reporter gene silencing. These results support a role of the Dicer-TRBP complex not only in miRNA processing but also as a platform for RISC assembly.
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PMID:TRBP recruits the Dicer complex to Ago2 for microRNA processing and gene silencing. 1597 56

Dicer is a key enzyme involved in RNA interference (RNAi) and microRNA (miRNA) pathways. It is required for biogenesis of miRNAs and small interfering RNAs (siRNAs), and also has a role in the effector steps of RNA silencing. Apart from Argonautes, no proteins are known to associate with Dicer in mammalian cells. In this work, we describe the identification of TRBP (human immunodeficiency virus (HIV-1) transactivating response (TAR) RNA-binding protein) as a protein partner of human Dicer. We show that TRBP is required for optimal RNA silencing mediated by siRNAs and endogenous miRNAs, and that it facilitates cleavage of pre-miRNA in vitro. TRBP had previously been assigned several functions, including inhibition of the interferon-induced double-stranded RNA-regulated protein kinase PKR and modulation of HIV-1 gene expression by association with TAR. The TRBP-Dicer interaction shown raises interesting questions about the potential interplay between RNAi and interferon-PKR pathways.
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PMID:TRBP, a regulator of cellular PKR and HIV-1 virus expression, interacts with Dicer and functions in RNA silencing. 1614 18


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