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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has previously been shown that the human immunodeficiency virus type 1 (HIV-1) trans-activation-responsive region (TAR) is contained in a stem-loop RNA structure. Moreover, the interaction of the RNA secondary structure with Tat, the trans-activator protein, seems to play a role in activation of transcription initiation and in preventing transcription attenuation. In this work, we have studied the ability of the HIV-1 TAR stem-loop to act as a specific attenuation signal for highly purified RNA polymerase II. We developed an in vitro system using dC-tailed DNA fragments of HIV-1 to study transcriptional control in the HIV-1 LTR. We have found that transcription in this system yields an attenuator RNA whose 3' end maps to the end of the TAR stem-loop, approximately 60 to 65 nucleotides downstream of the in vivo initiation site. Furthermore, transcription attenuation occurs only under conditions which cause displacement of the nascent transcript from the template DNA strand, thus allowing the RNA to fold into secondary structure. Evidence is provided that the purified polymerase II indeed recognizes stable RNA secondary structure as an intrinsic attenuation signal. The existence of this signal in the TAR stem-loop suggests that in vivo an antiattenuation factor, probably Tat, alone or in combination with other factors, acts to relieve the elongation block at the HIV-1 attenuation site.
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PMID:Transcriptional elongation by purified RNA polymerase II is blocked at the trans-activation-responsive region of human immunodeficiency virus type 1 in vitro. 187 Feb 6

Human immunodeficiency virus type 1 (HIV-1) is viable and mitogen inducible in the absence of its binding sites for the inducible transcription factor NF-kappa B. We have investigated alternative mechanisms for induction of HIV-1 transcription. Using transient transfection assays, we found that transcription from an HIV-1 LTR containing mutant kappa B sites was activated 10- to 20-fold in a variety of human cell types by the phorbol ester phorbol myristate acetate (PMA). The promoter elements conferring this inducibility were localized to the region downstream of nucleotide -70, which contains the TATA and TAR elements and binding sites for transcription factors Sp1 and LBP-1. Synthetic promoters containing only Sp1 sites and a TATA element were also induced in transfection experiments as well as in in vitro transcription experiments with T-cell nuclear extracts. Moreover, promoters containing a TATA box in the absence of Sp1 sites or Sp1 sites in the absence of a TATA box were equally inducible in vitro, as was an RNA polymerase III promoter. The activities of RNA polymerases II and III and of the 38-kDa TATA-binding protein transcription factor IID (TFIID), were not induced by PMA, but electrophoretic mobility shift assays revealed a highly inducible protein-DNA complex that interacted specifically with the TATA sequence. This protein-DNA complex appeared to be much larger than that found with the 38-kDa human TFIID expressed in bacteria. Taken together, these data suggest that a component of the general transcription machinery, and possibly a TFIID-associated protein, is induced in T cells by PMA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alternative pathway for induction of human immunodeficiency virus gene expression: involvement of the general transcription machinery. 189 93

Multiple binding of Tat and nuclear protein(s) to HIV-1 TAR RNA appears to be essential for the Tat-mediated trans-activation. As synthetic Tat-(1-47), which lacks the basic domain and does not bind TAR RNA in vitro, efficiently transactivated HIV-1 LTR in HeLa nuclear extracts, we hypothesized that Tat might trans-activate by interaction with TAR RNA via a host nuclear protein. The role of nuclear proteins in Tat-TAR interaction was examined through evaluation of several synthetic Tat peptides for ability to bind TAR RNA in vitro both in the presence and in the absence of HeLa nuclear proteins. Our data show that both Tat-(1-47) and Tat-(1-86) interact with TAR RNA-bound nuclear proteins, leading to dissociation of the nuclear protein-TAR RNA complexes; the N-terminal sequence of Tat appears to be involved in this interaction. Thus, after binding to TAR RNA, Tat can interact with a proximal TAR-bound nuclear protein and the resulting Tat-nuclear protein complex, now displaced from TAR, may initiate a facile and rapid assembly of the RNA polymerase II transcription complex. This study thus recognizes a novel interaction between Tat and a nuclear protein(s). Here we propose that the interaction of Tat with a nuclear protein(s) occurring on TAR RNA may be one of several steps in the mechanism of Tat-mediated trans-activation of the HIV-1 LTR.
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PMID:Synthetic HIV-1 Tat can dissociate HeLa nuclear protein-TAR RNA complexes in vitro: a novel Tat-nuclear protein interaction. 192 18

Using the method of Haseloff and Gerlach, we constructed a ribozyme specifically targeted against the virion infectivity factor (vif) of HIV-1. Both, the vif gene and an oligonucleotide representing the catalytic RNA sequence were cloned into pSPT19 downstream of the T7 promoter and transcribed with T7 RNA polymerase. Efficient cleavage of vif RNA by the synthetic ribozyme occurred at pH 7.5 and 37 degrees C in the presence of magnesium ions in vitro. No measurable activity was observed with a vif antisense RNA. A deletion in the hybridizing region of the ribozyme decreased the cleavage rate, while a mutation in the consensus cleavage domain abolished its catalytic activity. Thus, we could demonstrate an in-vitro activity of a specifically designed ribozyme against HIV-1 vif RNA.
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PMID:In vitro cleavage of HIV-1 vif RNA by a synthetic ribozyme. 201 74

Biological properties of an AIDS agent first isolated from a native citizen in the USSR are presented. The source of the virus was a young Byelorussian woman who in the near past had had sexual contacts with a citizen from one of the Central Africa countries. The isolate is thought to be of HIV-I type. It replicated perfectly in many continuous lymphocyte lines and had HIV-characteristic morphology. The protein spectrum of the isolate was gp120, gp41, p65/51, p55, p32, p24, p17. Reverse transcriptase activity was detected in the culture fluid of the virus-containing cell cultures. The isolate was designated HIV-IZ.
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PMID:[The biological properties of the HIV isolated from a virus carrier living in the Byelorussian SSR]. 214 58

An enzyme immunoassay was developed to detect human immunodeficiency virus type 1 (HIV-1) DNA amplified by polymerase chain reaction (PCR-EIA). A set of primers (outer set) was used in PCR to amplify a segment of the HIV-1 gag gene from peripheral blood mononuclear cells. Hybrids between the amplified DNA and a RNA probe were measured in a microtiter plate immunoassay using a beta-D-galactosidase-conjugated monoclonal antibody to DNA-RNA hybrids and a fluorescent substrate. A second set of primers (nested set) located within the outer set was used in PCR with a known template to prepare the probe. One primer of the nested set included the T7 RNA polymerase promoter at its 5' end allowing transcription of a single-stranded RNA probe. Ten copies of HIV-1 DNA could be detected by PCR-EIA (42 fluorescent units with a background of 18 fluorescent units) compared with a detection limit of 1000 copies by ethidium bromide-stained agarose gel. HIV-1 DNA was detected by PCR-EIA in peripheral blood mononuclear cells from 32 of 33 seropositive patients (range 54-810 fluorescent units), and 0 of 25 seronegative patients (range 20-40 fluorescent units) (sensitivity 97%; specificity 100%). PCR-EIA offers a practical and nonisotopic method to objectively measure PCR-amplified HIV-1 DNA and has the potential for the measurement of other microbial pathogens in human body fluids.
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PMID:Enzyme immunoassay for detection of hybrids between PCR-amplified HIV-1 DNA and a RNA probe: PCR-EIA. 174 86

Regulation of eukaryotic genes is largely governed by multiple cis-acting DNA sequences recognized by specific transcription factors. The transcription factor NF-kappa B has been implicated as an important regulator of cellular and viral genes, including those of immunoglobulin kappa light chain, interleukin-2, beta-interferon, HIV-1 and cytomegalovirus. We have analyzed the effect of increasing the number of NF-kappa B sites, located directly upstream from the TATA box. Four copies of the sequence gave a more than 100-fold stimulation relative to a single copy, suggesting that NF-kappa B proteins act synergistically to bring about this dramatic increase in transcription. By DNase I footprinting we demonstrated factor binding to two adjacent NF-kappa B sites in vitro. However, we found no evidence for co-operative binding to these DNA sites. We propose that the high transcriptional activity results from another type of co-operation, based on multiple weak interactions of the NF-kappa B factors with another component of the transcription apparatus, perhaps RNA polymerase II itself.
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PMID:Synergistic activation of transcription by multiple binding sites for NF-kappa B even in absence of co-operative factor binding to DNA. 219 80

We describe an unusual element that activates the synthesis of short transcripts from a wide variety of mRNA and small nuclear RNA (snRNA) promoters, including the U6 RNA polymerase III promoter. This inducer of short transcripts (IST) is located between positions -5 and +82 relative to the cap site in the HIV-1 LTR. In the presence of IST, the total transcriptional activity of the different promoters is greatly increased, but the resulting additional RNA molecules are short, ending around position +60. IST is not the RNA target (TAR) for Tat trans-activation; however, because it relies entirely on cellular factors for activity, IST may serve to provide abundant RNA targets for Tat trans-activation without a requirement for full-length viral mRNA expression.
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PMID:The HIV-1 long terminal repeat contains an unusual element that induces the synthesis of short RNAs from various mRNA and snRNA promoters. 226 26

Four flavonoids (i.e., baicalein, quercetin, quercetagetin, and myricetin), known to be inhibitors of HIV-reverse transcriptase, have been shown to be more or less inhibitory to the activities of various cellular DNA and RNA polymerases. The degree of the inhibition varied depending on the combination of the flavonoid and the enzyme species: baicalein was moderately inhibitory to DNA polymerase gamma and E. coli DNA polymerase I; quercetin was strongly inhibitory to DNA polymerase beta and E. coli RNA polymerase and moderately inhibitory to DNA polymerase I; quercetagetin was a potent inhibitor for all of DNA polymerases alpha, beta, gamma, and I and RNA polymerase; myricetin was a strong inhibitor of DNA polymerases alpha and I and RNA polymerase. However, terminal deoxynucleotidyltransferase was virtually insensitive to inhibition by these flavonoids. The inhibition by the flavonoids was due to competition with the template.primer in the case of the DNA polymerases, whereas the inhibition was due to competition with the triphosphate substrate (GTP) in the case of RNA polymerase. The Ki values of these flavonoid inhibitors for DNA and RNA polymerases was determined.
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PMID:Mechanisms of inhibition of various cellular DNA and RNA polymerases by several flavonoids. 229 90

We have investigated the effects of HIV-1 infection on cellular gene expression in two different human CD4 positive lymphoid cell lines: CEM and C8166 cells. As a prerequisite for this study it was necessary to develop virus-cell culture systems in which greater than 90% of the cells could be near synchronously infected by HIV-1. Further, since HIV-1 is a cytopathic virus, it was essential that cellular gene expression be examined in virus-infected cells which remained viable. After meeting these requirements, we measured cellular RNA and protein levels in virus-infected lymphocytes. In the cell lines examined the levels of cellular protein synthesis markedly decreased at times when viral-specific protein synthesis was increasing. Both Northern and slot blot analysis revealed that the declines in host protein synthesis were due, at least in part, to declines in steady state levels of cellular mRNAs. Runoff assays with nuclei isolated from infected cells demonstrated that the decreases in cellular mRNA levels were not due to declines in cellular RNA polymerase II transcription rates. To determine if the decreases in cellular protein synthesis also might be due to specific translational controls exerted by HIV-1, we compared the polysome association of cellular RNAs in infected and uninfected C8166 cells. The polysome distribution of cellular mRNAs was virtually identical in mock- and HIV-1-infected cells although, as expected, the total amount of cellular mRNAs were significantly lower in virus-infected cells. Taken together, these results suggest that HIV-1 may encode mechanisms to inhibit cellular protein synthesis, likely as a result of cellular mRNA degradation, rather than specific blocks in cellular mRNA translation.
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PMID:Expression of cellular genes in CD4 positive lymphoid cells infected by the human immunodeficiency virus, HIV-1: evidence for a host protein synthesis shut-off induced by cellular mRNA degradation. 235 54


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