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)

U-75875 inhibits human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus (SIV) proteases and blocks Gag-Pol protein processing and viral maturation and replication in vitro. Rhesus monkeys were treated with vehicle alone or with formulated U-75875 at doses of 7 or 20 mg/kg of body weight per day for 26 days by continuous intravenous infusion beginning 6 h prior to intravenous inoculation with 10 monkey 50% infectious doses of SIV Delta B670, and the monkeys were monitored until death. The effects of treatment on the level of SIV p26 antigenemia, the infectious virus titer in serum, and the level of proviral DNA in blood mononuclear cells evaluated by PCR were assessed. SIV infection of the controls resulted in an initial viral antigenemia that began 5 to 10 days postinoculation (p.i.), reached peak values on days 10 to 14 p.i., and lasted for more than 15 days. Proviral DNA was detectable in peripheral blood mononuclear cells by 7 to 11 days p.i., reached the mean peak level by 11 days p.i., and remained at high levels through day 24 p.i. Infectious virus was detected in serum from all of the infected controls by 24 days p.i. Treatment with U-75875 for 26 days resulted in a dose-related delay in the day of the peak level of antigenemia (P = 0.034). The level of proviral DNA in peripheral blood mononuclear cells at 11 days p.i. was significantly decreased in a dose-related fashion in the treated monkeys ( P </- 0.048), with a delay in the attainment of the peak level of proviral DNA in the treated groups. The titer of infectious virus in the serum of the group treated with 20 mg/kg/day was significantly decreased on day 24 p.i. compared with that in the serum of controls ( P = 0.046). Treatment with formulated U-75875 was well tolerated in rhesus monkeys and resulted in an inhibitory effect of SIV in vivo.
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PMID:Effects of U-75875, a peptidomimetic inhibitor of retroviral proteases, on simian immunodeficiency virus infection in rhesus monkeys. 752 27

The overlapping region of gag and pol genes of human immunodeficiency virus type 1 (HIV-1) also called transframe region, contains the frameshift locus from gag to pol. This region encodes both the protein p6, the function of which remains unclear, and a putative transframe protein covently linked to the N-terminus of the viral protease within Gag/Pol protein precursor. We have investigated the variability of the transframe region among nine HIV-1 isolates obtained from Congolese AIDS patients. Nucleotide sequences were determined using the polymerase chain reaction and the direct sequencing of amplified products. The sequences of Congolese isolates markedly differed from one another and from other reference HIV-1 strains by both insertion-deletion events and numerous base substitutions. Several putative cleavage sites of precursor polypeptides were modified. When compared to consensus ones the amino acid sequences of p6 protein were very different among divergent HIV-1 isolates, except for a limited group of 10 conserved amino acids.
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PMID:High variability of the gag/pol transframe region among HIV-1 isolates. 799 8

Analysis of the complete sequence of a human immunodeficiency virus (HIV) isolate (Ant70) obtained from a Cameroonian patient indicates that this virus is the most divergent strain within the HIV-1 family hitherto described. Comparison of the Pol protein, usually highly conserved within the HIV-1 family, shows only about 73% similarity with the HIVmm isolate, whereas for the more variable proteins such as envelope, similarities of 50% or lower are found. The principal neutralizing determinant (V3 loop) and the immunodominant region within gp41 also contain some unusual substitutions, which may have implications for protein function as well as for serological assays based on these regions. Phylogenetic analyses show that this isolate occupies a unique position relative to the human HIV-1 isolates and the recently described SIVcpz virus, indicating that this Cameroonian isolate may provide us with new insights into the origins of the HIV-1 family.
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PMID:Genomic cloning and complete sequence analysis of a highly divergent African human immunodeficiency virus isolate. 810 20

Factors that modulate the placement of primer tRNA(3Lys) onto the viral RNA genome in human immunodeficiency virus type 1 (HIV-1) were investigated through analysis of reverse-transcribed products that are extended from the tRNA(3Lys) primer. Mutations were introduced into the HIV-1 pol gene to result in the appearance of a stop codon in the open reading frame of the reverse transcriptase (RT) gene. These constructs, BH10-RT1 and BH10-RT2, yielded viruses with truncated Pol proteins. Alternatively, we altered the sequences involved in frameshifting by generating the construct BH10-FS. With each of these mutated viruses, we found that the primer tRNA(3Lys) that was placed onto viral genomic RNA was present in an unextended state. In contrast, as expected, tRNA(3Lys) in the case of wild-type BH10 virus had been extended by 2 bases. Furthermore, the amount of tRNA(3Lys) that was placed onto viral RNA in mutated viruses was significantly less than that placed in the wild-type virus. We also generated a mutant within the polymerase-active site of RT (D185H) (Asp-->His) that eliminated RT polymerase activity. We found that the placement of primer tRNA(3Lys) onto viral genomic RNA was independent of enzyme function; however, the tRNA(3Lys) that was placed was present in an unextended state due to the loss of RT activity. In contrast, the elimination of protease activity through a D25A (Asp-->Ala) point mutation in the protease-active site (construct BH10-PR) did cause a drop in the efficiency of tRNA(3Lys) placement. In this situation, a proportion of the placed tRNA(3Lys) was found to be extended by 2 bases, although not to the extent found with wild-type virus (BH10), due to a decrease in RT activity associated with unprocessed Gag-Pol protein that could not be cleaved because of the loss of protease activity. We also investigated the role of the primer binding site (PBS) in the placement of tRNA(3Lys) through a series of 2-, 4-, and 8-nucleotide (nt) deletions at the 3' end of the PBS, i.e., BH10-PBS2, BH10-PBS4, and BH10-PBS8, respectively. In mutated viruses BH10-PBS2 and BH10-PBS4, the 2-base-extended form of tRNA(3Lys) was still detected. However, less primer tRNA(3Lys) was placed onto viral genomic RNA as more nucleotides were deleted until the percentage of placement seen with wild-type BH10 virus dropped to only 4% in the virus with 8 nt deleted (BH10-PBS8). Consistently, these mutated viruses possessed decreased initial replication capacity compared with that of the wild-type virus, with the extent of incapacity corresponding to the size of the deletion. However, after several days, an increase in replication potential was accompanied by a reversion to a wild-type PBS.
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PMID:The roles of the human immunodeficiency virus type 1 Pol protein and the primer binding site in the placement of primer tRNA(3Lys) onto viral genomic RNA. 937 64

Synthesis of the Gag-Pol protein of the human immunodeficiency virus type 1 (HIV-1) requires a programmed -1 ribosomal frameshifting when ribosomes translate the unspliced viral messenger RNA. This frameshift occurs at a slippery sequence followed by an RNA structure motif that stimulates frameshifting. This motif is commonly assumed to be a simple stem-loop for HIV-1. In this study, we show that the frameshift stimulatory signal is more complex than believed and consists of a two-stem helix. The upper stem-loop corresponds to the classic stem-loop, and the lower stem is formed by pairing the spacer region following the slippery sequence and preceding this classic stem-loop with a segment downstream of this stem-loop. A three-purine bulge interrupts the two stems. This structure was suggested by enzymatic probing with nuclease V1 of an RNA fragment corresponding to the gag/pol frameshift region of HIV-1. The involvement of the novel lower stem in frameshifting was supported by site-directed mutagenesis. A fragment encompassing the gag/pol frameshift region of HIV-1 was inserted in the beginning of the coding sequence of a reporter gene coding for the firefly luciferase, such that expression of luciferase requires a -1 frameshift. When the reporter was expressed in COS cells, mutations that disrupt the capacity to form the lower stem reduced frameshifting, whereas compensatory changes that allow re-formation of this stem restored the frameshift efficiency near wild-type level. The two-stem structure that we propose for the frameshift stimulatory signal of HIV-1 differs from the RNA triple helix structure recently proposed.
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PMID:Characterization of the frameshift stimulatory signal controlling a programmed -1 ribosomal frameshift in the human immunodeficiency virus type 1. 1246 32

Cells normally restrict the nuclear export and expression of intron-containing mRNA. In many cell lines, this restriction can be overcome by inclusion of cis-acting elements, such as the Mason-Pfizer monkey virus constitutive transport element (CTE), in the RNA. In contrast, we observed that CTE-mediated expression from human immunodeficiency virus Gag-Pol reporters was very inefficient in 293 and 293T cells. However, addition of Sam68 led to a dramatic increase in the amount of Gag-Pol proteins produced in these cells. Enhancement of CTE function was not seen when a Sam68 point mutant (G178E) that is defective for RNA binding was used. Additionally, the effect of Sam68 was inhibited in a dose-dependent manner by coexpression of an activated form of the nuclear kinase Sik/BRK that hyperphosphorylated Sam68. RNA analysis showed that cytoplasmic Gag-Pol-CTE RNA levels were only slightly enhanced by the addition of Sam68, compared to a 60- to 70-fold increase in the levels of Gag-Pol protein expression. Thus, in this system, Sam68 functioned to enhance the cytoplasmic utilization of RNA containing the CTE. These results suggest that Sam68 may interact with specific RNAs in the nucleus to provide a "mark" that affects their cytoplasmic fate. They also provide further evidence of links between signal transduction and RNA utilization.
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PMID:Sam68 enhances the cytoplasmic utilization of intron-containing RNA and is functionally regulated by the nuclear kinase Sik/BRK. 1248 64

We investigated the role of 5' untranslated leader sequences of simian immunodeficiency virus (SIV(mac239)) in RNA encapsidation and protein expression. A series of progressively longer deletion mutants was constructed with a common endpoint six nucleotides upstream of the gag initiation codon and another endpoint at the 3' end of the primer binding site (PBS). We found that efficient intracellular Gag-Pol protein accumulation required the region between the PBS and splice donor (SD) site. Marked reduction of genomic RNA packaging was observed with all the deletion mutants that involved sequences at both the 5' and at the 3' ends of the major SD site, and increased nonspecific RNA incorporation could be detected in these mutants. RNA encapsidation was affected only modestly by a deletion of 54 nucleotides at the 3' end of the SD site when the mutant construct pDelta54 was transfected alone. In contrast, the amount of pDelta54 genomic RNA incorporated into particles was reduced more than 10-fold when this mutant was cotransfected with a construct specifying an RNA molecule with a wild-type packaging signal. Therefore, we conclude that the 175 nucleotides located 5' of the gag initiation codon are critical for efficient and selective incorporation of genomic RNA into virions. This location of the SIV Psi element provides the means for efficient discrimination between viral genomic and spliced RNAs.
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PMID:The simian immunodeficiency virus 5' untranslated leader sequence plays a role in intracellular viral protein accumulation and in RNA packaging. 1274 85

By using particle-associated reverse transcriptase (RT) activity as an assay for Pol incorporation into human immunodeficiency virus type 1 (HIV-1) Gag virus-like particles (VLPs), it has been found that truncated, protease-negative, Gag-Pol missing cis Gag sequences is still incorporated into Gag VLPs, albeit at significantly reduced levels (10 to 20% of the level of wild-type Gag-Pol). In this work, we have directly measured the incorporation of truncated Gag-Pol species into Gag VLPs and have found that truncated Gag-Pol that is missing all sequences upstream of RT is still incorporated into Gag VLPs at levels approximating 70% of that achieved by wild-type Gag-Pol. Neither protease nor integrase regions in Pol are required for its incorporation, implying an interaction between Gag and RT sequences in the Pol protein. While the incorporation of Gag-Pol into Gag VLPs is reduced 12-fold by the replacement of the nucleocapsid within Gag with a leucine zipper motif, this mutation does not affect Pol incorporation. However, the deletion of p6 in Gag reduces Pol incorporation into Gag VLPs four- to fivefold. Pol shows the same ability as Gag-Pol to selectively package tRNA(Lys) into Gag VLPs, and primer tRNA(3)(Lys) is found annealed to the viral genomic RNA. These data suggest that after the initial separation of Gag from Pol during cleavage of Gag-Pol by viral protease, the Pol species still retains the capacity to bind to both Gag and tRNA(3)(Lys), which may be required for Pol and tRNA(3)(Lys) to be retained in the assembling virion until budding is completed.
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PMID:Incorporation of pol into human immunodeficiency virus type 1 Gag virus-like particles occurs independently of the upstream Gag domain in Gag-pol. 1469 38

L'Hoest's monkey's (Cercopithecus Ihoesti) are believed to be naturally infected with a simian immunodeficiency virus (SIV), termed SIVIho, but only a handful of isolates, all derived from captive animals from the Democratic Republic of Congo (DCR), have thus far been characterized. Here, we report the noninvasive detection and molecular characterization of SIVIho in a wild L'Hoest's monkey from the Nyungwe Forest in Rwanda. Screening four L'Hoest's monkey fecal samples collected opportunistically as part of a larger noninvasive survey of SIV prevalence in Nyungwe National Park we identified one to be vRNA positive. Reverse transcriptase polymerase chain reaction (RT-PCR) amplification of a subgenomic pol fragment (598 bp) identified a new SIVIho strain (RW30) that differed from previously reported SIVIho isolates in 17-22% of its nucleotide sequence. In a phylogenic tree of partial Pol protein sequences, RW30 fell well within the SIVIho radiation, but was not particularly closely related to any of the other strains. These results provide the first direct evidence that L'Hoewst's monkeys harbor SIVIho in the wild, that infection is prevalent in different areas of the species' habitat, and that geographically diverse SIVIho strains cluster in a single group according to their species of origin. L'Hoest's monkeys represent the third primate species for which the utility of noninvasive SIV testing has been documented.
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PMID:Noninvasive detection of Simian immunodeficiency virus infection in a wild-living L'Hoest's monkey (Cercopithecus Ihoesti). 1471 18

Nearly complete sequences of simian immunodeficiency viruses (SIVs) infecting 18 different nonhuman primate species in sub-Saharan Africa have now been reported; yet, our understanding of the origins, evolutionary history, and geographic distribution of these viruses still remains fragmentary. Here, we report the molecular characterization of a lentivirus (SIVdeb) naturally infecting De Brazza's monkeys (Cercopithecus neglectus). Complete SIVdeb genomes (9,158 and 9227 bp in length) were amplified from uncultured blood mononuclear cell DNA of two wild-caught De Brazza's monkeys from Cameroon. In addition, partial pol sequences (650 bp) were amplified from four offspring of De Brazza's monkeys originally caught in the wild in Uganda. Full-length (9068 bp) and partial pol (650 bp) SIVsyk sequences were also amplified from Sykes's monkeys (Cercopithecus albogularis) from Kenya. Analysis of these sequences identified a new SIV clade (SIVdeb), which differed from previously characterized SIVs at 40 to 50% of sites in Pol protein sequences. The viruses most closely related to SIVdeb were SIVsyk and members of the SIVgsn/SIVmus/SIVmon group of viruses infecting greater spot-nosed monkeys (Cercopithecus nictitans), mustached monkeys (Cercopithecus cephus), and mona monkeys (Cercopithecus mona), respectively. In phylogenetic trees of concatenated protein sequences, SIVdeb, SIVsyk, and SIVgsn/SIVmus/SIVmon clustered together, and this relationship was highly significant in all major coding regions. Members of this virus group also shared the same number of cysteine residues in their extracellular envelope glycoprotein and a high-affinity AIP1 binding site (YPD/SL) in their p6 Gag protein, as well as a unique transactivation response element in their viral long terminal repeat; however, SIVdeb and SIVsyk, unlike SIVgsn, SIVmon, and SIVmus, did not encode a vpu gene. These data indicate that De Brazza's monkeys are naturally infected with SIVdeb, that this infection is prevalent in different areas of the species' habitat, and that geographically diverse SIVdeb strains cluster in a single virus group. The consistent clustering of SIVdeb with SIVsyk and the SIVmon/SIVmus/SIVgsn group also suggests that these viruses have evolved from a common ancestor that likely infected a Cercopithecus host in the distant past. The vpu gene appears to have been acquired by a subset of these Cercopithecus viruses after the divergence of SIVdeb and SIVsyk.
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PMID:New simian immunodeficiency virus infecting De Brazza's monkeys (Cercopithecus neglectus): evidence for a cercopithecus monkey virus clade. 1522 Apr 49


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