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)

The mechanism by which Rev facilitates the export, and consequently, the translation of the structural protein mRNAs of the human immunodeficiency virus type 1 remains undefined. Previous immunolocalization has determined that Rev is predominantly in the nucleus with significant accumulation in the nucleolus, a localization consistent with the assumed site of Rev action. To determine whether the subcellular distribution is more dynamic than what was indicated by the original studies, the capacity of Rev to shuttle between the nucleus and cytoplasm was examined. It was observed that treatment of cells with DRB or actinomycin D resulted in a dramatic alteration in Rev distribution, the majority of the protein being found in the cytoplasm. Removal of the drug resulted in a rapid accumulation of Rev in the nucleus indicating that the block to nuclear import was reversible. Subsequent studies indicated that the movement of Rev into the cytoplasm was a passive process while its accumulation in the nucleus was an active one, given that only the latter displayed sensitivity to temperature. Finally, it was demonstrated that, while extensive redistribution of Rev could be attained by inhibition of RNA polymerase I alone, Rev was still capable of inducing expression of HIV structural gene expression under these conditions. Consequently, Rev activity does not appear to be dependent on either an intact nucleolus or the accumulation of the protein in the nucleus.
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PMID:HIV-1 Rev is capable of shuttling between the nucleus and cytoplasm. 809 47

The presence of HIV provirus in the cell culture and in the patients' blood was studied by polymerase chain reaction followed by hybridization in solution. It was shown that: (i) the hybridized product could be detected both by gel electrophoresis and by binding on hydroxyapatite; (ii) the detection level achieved was no more than 10 infected lymphocytes per million; (iii) the hybridization signal and sensitivity of detection could be enhanced by the transcription of PCR product by the phage T7 RNA polymerase. The observed lack of complete correlation between the amount of provirus and of the p24 antigen in the patients' blood possibly reflects the peculiarities of HIV infection.
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PMID:[The detection of provirus in lymphocyte DNA. The monitoring of HIV infection at the genetic level]. 809 47

In order to investigate the role of germ cells in the sexual transmission of immunodeficiency virus (HIV), spermatozoa from healthy HIV-seronegative men were incubated in vitro with HIV1. After washing, they were cocultured with peripheral blood leukocytes from seronegative blood donors. Reverse transcriptase assays and p24 antigen tests were performed in culture supernatants. Electron microscopy examination of these HIV-incubated spermatozoa was carried out, as well as the search for CD4 molecules on their surface. Although virus bound to and seemed to enter spermatozoa despite the absence of detectable CD4 epitopes on their surface, no replication of HIV was apparent. However, HIV particles on the surface of spermatozoa were capable of infecting CD4 T lymphocytes. Present results would seem to preclude artificial insemination between an HIV-seropositive man and an HIV-seronegative woman.
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PMID:Spermatozoa as potential carriers of HIV. 814 Feb 92

Drug-resistant tuberculosis has become a major public health problem. Resistance to rifampicin probably arises through mutations in the mycobacterial RNA polymerase. Patients may acquire rifampicin resistant tuberculosis by three mechanisms: (1) infection with a resistant organism, (2) selection of a sub-population of resistant organisms that remain contained whilst the more virulent wild type is present, (3) mutations within the population of bacilli causing the original infection. Sequential isolates of Mycobacterium tuberculosis were collected from 2 patients who developed rifampicin resistance whilst on treatment. One patient was immunosuppressed with HIV-infection; in the other patient the original isolate was also resistant to isoniazid. DNA fingerprinting techniques were used to type the isolates. No differences were found between the fingerprints of isolates from before and after the development of resistance. These data suggest that the third of the mechanisms listed above was responsible for the acquisition of rifampicin resistance in these 2 patients.
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PMID:DNA fingerprints of Mycobacterium tuberculosis do not change during the development of rifampicin resistance. 791 47

The control of HIV-1 gene expression depends upon interaction of Tat with the trans-activation responsive (TAR) element present at the 5' end of all HIV-1 transcripts. The TAR sequence forms a stable hair-pin structure that binds Tat and several cellular factors in vitro. In the absence of Tat, TAR acts as a transcription terminator. Tat in conjunction with a cellular factor(s) acts to increase the elongation capacity of the transcription complex. Here we report that Ku protein, the autoantigen in patients with systemic lupus erythematosus, binds TAR RNA in vitro with high affinity and specificity forming a single protein-RNA complex. Ku, a heterodimer of Ku72 and Ku86 that non-specifically binds the ends of DNA fragments, appears to recognize the terminal loop of TAR RNA. UV-crosslinking showed that both subunits of Ku are in proximity to the RNA. Further, Ku shows a 5-fold higher affinity for TAR RNA than for the ends of dsDNA. As Ku is involved in the stimulation of the elongation property of the RNA polymerase II and activation of several transcription factors, the specific interaction of Ku with TAR raises intriguing possibilities for its function in HIV-1 gene expression.
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PMID:Lupus autoantigen Ku protein binds HIV-1 TAR RNA in vitro. 824 Mar 70

Regulation of transcriptional elongation is emerging as an important control mechanism for eukaryotic gene expression. In this essay, we review the basis of the current view of the regulation of elongation in the human c-myc gene and discuss similarities in elongation control among the c-myc, Drosophila hsp70 and the HIV-1 genes. Based upon these similarities, we propose a model for control of expression of these genes at the elongation phase of transcription. This model suggests that distinct promoter elements direct the assembly of RNA polymerase II transcription complexes which differ in their elongation efficiency.
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PMID:Common mechanisms for the control of eukaryotic transcriptional elongation. 827 41

Antiterminator proteins control gene expression by recognizing control signals near the promoter and preventing transcriptional termination which would otherwise occur at sites that may be a long way downstream. The N protein of bacteriophage lambda recognizes a sequence in the nascent RNA, and modifies RNA polymerase by catalysing the formation of a stable ribonucleoprotein complex on its surface, whereas the lambda Q protein recognizes a sequence in the DNA. These mechanisms of antitermination in lambda provide models for analysing antitermination in viruses such as HIV-1 and in eukaryotic genes.
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PMID:Transcriptional antitermination. 833 11

A hammerhead ribozyme designed to cleave in trans the R region of HIV-1 RNA was inserted into a eukaryotic expression vector. This ribozyme was studied in vitro using the T3 RNA polymerase promoter located upstream of the eukaryotic promoter. The ribozyme showed no activity against its specific target sequence under any condition tested. To decrease the influence of potential cis inhibitory sequences in such a ribozyme transcript, a specific target sequence was inserted upstream of the ribozyme-coding sequence. This insertion allowed the release by cis cleavage of a short RNA bearing ribozyme activity and able to cleave in trans an external RNA target. The cis cleavage reaction generated two RNA molecules: the shorter RNA species, which included the catalytic domain, showed a trans cleavage reaction. This self-cleavable ribozyme was active in vitro at 37 degrees C against three distinct HIV-1 transcripts sharing the specific target sequence. Ribozyme activity was thus attained by self-cleavage of the ribozyme-containing sequence from the longer vector transcript.
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PMID:Activation of HIV-specific ribozyme activity by self-cleavage. 834 99

The human immunodeficiency virus type 1 (HIV-1) Vpu protein is a transmembrane phosphoprotein which induces rapid degradation of CD4 in the endoplasmic reticulum (ER). To identify sequences in CD4 for Vpu-induced degradation, we generated four chimeric envelope glycoproteins having the ectodomain of HIV-1 gp160, the anchor domain of CD4, and 38, 25, 24, and 18 amino acids (aa) of the CD4 cytoplasmic domain. Using the vaccinia virus-T7 RNA polymerase expression system, we analyzed the expression of chimeric proteins in the presence and absence of Vpu. In singly transfected cells, the chimeric envelope glycoproteins having 38, 24, and 18 aa of the CD4 cytoplasmic domain were endoproteolytically cleaved and biologically active in the fusion of HeLa CD4+ cells. However, one of the chimeras having 25 aa of the CD4 cytoplasmic tail was retained in the ER using the transmembrane ER retention signal and was defective in membrane fusion. Furthermore, biochemical analyses of the coexpressing cells revealed that the Vpu protein induced degradation of the envelope glycoproteins having 38, 25, and 24 aa of the CD4 cytoplasmic tail and degradation occurred in the ER. Consequently, the fusion-competent glycoproteins did not induce the formation of syncytia in HeLa CD4+ cells expressing Vpu. However, the HIV-1 gp160 and chimeric envelope glycoprotein having the membrane-proximal 18 aa of the CD4 cytoplasmic tail were stable and fusion competent in cells expressing Vpu. In addition, we examined the stability of CD4 molecules in the presence of Vpu. Coexpression analyses revealed that the Vpu protein induced degradation of CD4 whereas mutant CD4 having the membrane-proximal 18 aa of the cytoplasmic domain was relatively stable in the presence of Vpu. Taken together, these studies have elucidated that the Vpu protein requires sequences or sequence determinants in the cytoplasmic domain of CD4 to induce degradation of the glycoproteins in the cell.
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PMID:Human immunodeficiency virus type 1 Vpu protein induces degradation of chimeric envelope glycoproteins bearing the cytoplasmic and anchor domains of CD4: role of the cytoplasmic domain in Vpu-induced degradation in the endoplasmic reticulum. 835 Apr 11

The HIV-1 Tat protein enhances the formation of productive RNA polymerase II elongation complexes, potentially acting through a positive-acting, DRB-sensitive elongation factor. Tat is usually recruited to the HIV-1 promoter through the Tat trans-activation response element RNA stem-loop structure; however, recent data suggest that in certain cell types it can be directed instead through upstream enhancer elements. New studies also reveal that the response element overlaps a novel motif that promotes the assembly of abortive elongation complexes in the absence of Tat.
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PMID:Tat and the HIV-1 promoter. 835 64


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