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At least 253 records · Page 14Linked to original sources
PubMed1998

Replication of human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus strain mac (SIVmac) and chimeric HIV-1/SIVmac viruses having env genes derived from macrophage-tropic viruses: an indication of different mechanisms of macrophage-tropism in human and monkey cells.

To investigate the transferability of macrophage (Mphi)-tropism among primate lentiviruses, we constructed recombinants of human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus strain mac (SIVmac) and chimeric HIV-1/SIVmac (SHIV) having env region Mphi-tropic determinants. A recombinant HIV-1 having env partially derived from a Mphi-tropic HIV-1 strain (JR-FL) replicated in human macrophages but not in monkey macrophages. Conversely, a recombinant SIVmac having env from a Mphi-tropic strain (SIVmac316) replicated in monkey macrophages but not in human macrophages. A new SHIV (designated NM-3rN/JRFL) carrying the LTR and gag, pol, vif, vpx and nef of SIVmac and vpr, tat, rev, vpu and env of HIV-1 with env partially replaced by that of JR-FL was replication-competent in human macrophages but not in monkey macrophages. These results suggest that the Mphi-tropic determinant is specific to each host species and that the mechanism of Mphi-tropism is different between HIV and SIV.

Animals↗
PubMed1992

Mutations within the env gene of Mason-Pfizer monkey virus: effects on protein transport and SU-TM association.

By deletion mutagenesis analyses, we have examined the contribution of the immunosuppressive peptide (ISP) region within the transmembrane (TM) protein of Mason-Pfizer monkey virus to viral maturation and infectivity. Deletion of the entire region (mutant D105) results in the production of an Env precursor that is transport defective and therefore unable to be processed to mature glycoproteins. This mutation results in the release of noninfectious virions devoid of surface glycoproteins. A second deletion that removes the most highly conserved 11 amino acids of the ISP (mutant D33) does not affect the production, transport, or processing of the Env precursor yet produces virions that are noninfectious. The mutation was shown to cause the loss of interaction between the surface (SU) and TM proteins and result in the efficient shedding of gp70 into the culture medium. The released gp70 protein was biologically active and could still bind with high specificity to susceptible target cells. Since the ISP domain may represent an area of contact between SU and TM, it could provide an additional explanation for the amino acid sequence homology observed within this region of a variety of retroviruses.

Amino Acid Sequence↗
PubMed1999

Host-specific modulation of the selective constraints driving human immunodeficiency virus type 1 env gene evolution.

To address the evolution of human immunodeficiency virus type 1 (HIV-1) within a single host, we analyzed the HIV-1 C2-V5 env regions of both cell-free genomic-RNA- and proviral-DNA-derived clones. Sequential samples were collected over a period of 3 years from six untreated subjects (three typical progressors [TPs] and three slow progressors [SPs], all with a comparable length of infection except one. The evolutionary analysis of the C2-V5 env sequences performed on 506 molecular clones (253 RNA- and 253 DNA-derived sequences) highlighted a series of differences between TPs and SPs. In particular, (i) clonal sequences from SPs (DNA and RNA) showed lower nucleotide similarity than those from TPs (P = 0. 0001), (ii) DNA clones from SPs showed higher intra- and intersample nucleotide divergence than those from TPs (P < 0.05), (iii) higher host-selective pressure was generally detectable in SPs (DNA and RNA sequences), and (iv) the increase in the genetic distance of DNA and RNA sequences over time was paralleled by an increase in both synonymous (Ks) and nonsynonymous (Ka) substitutions in TPs but only in nonsynonymous substitutions in SPs. Several individual peculiarities of the HIV-1 evolutionary dynamics emerged when the V3, V4, and V5 env regions of both TPs and SPs were evaluated separately. These peculiarities, probably reflecting host-specific features of selective constraints and their continuous modulation, are documented by the dynamics of Ka/Ks ratios of hypervariable env domains.

Base Sequence↗
PubMed2003

Quantitation of HERV-K env gene expression and splicing in human breast cancer.

Human endogenous retroviruses (HERVs) comprise up to 8% of the human genome. In previous studies, we demonstrated that type 1 HERV-K envelope (env) transcripts are expressed in most human breast cancers, but not in normal breast tissues. In the current study, we report that type 2 HERV-K env transcripts are also present in human breast cancers. By real-time RT-PCR, the expression of HERV-K env transcripts was 5-10-fold higher in breast cancer cell lines treated with estradiol and progesterone than in cells without treatment, and expression was significantly higher in most breast cancer tissues than in normal breast tissues. Furthermore, both types of HERV-K env transcripts were capable of being spliced into subgenomic env transcripts and various splice donor and acceptor sites were detected in breast cancers. The selective expression and distribution of multiple HERV-K endogenous retroviral element splice variants in breast cancer, but not in normal controls, suggests that they are novel breast tumor markers.

Breast Neoplasms↗
PubMed2003

Specific HIV-1 env gene silencing by small interfering RNAs in human peripheral blood mononuclear cells.

RNA interference (RNAi) is triggered by the presence of a double-stranded RNA (dsRNA) in the cell, and results in the silencing of homologous gene expression by the specific degradation of an mRNA containing the same sequence. dsRNA-mediated RNAi can be used in a wide variety of eucaryotes to induce the sequence-specific inhibition of gene expression. Synthetic 21-23 nucleotide (nt) small interfering RNAs (siRNAs) with 2-nt 3' overhangs were recently found to mediate efficient sequence-specific mRNA degradation in mammalian cells. Here, we show that synthetic siRNAs targeted against the viral structural Env proteins encoded by HIV-1 can specifically suppress the expression of HIV-1 genes. The siRNA-mediated RNAi also had advantages over antisense RNA-mediated inhibition, in terms of both the ease of designing effective antiviral agents and their potency. Especially, our best env-specific siRNAs, E7145 targeted to the central region of the V3 loop and E7490 targeted to the CD4 binding site of conserved regions on gp120, significantly inhibited the HIV-1 gene expression. Furthermore, E7145 and E7490 were effective against HIV-1(NL4-3) replication in PBMCs for a relatively long time (14 days). Therefore, the use of synthetic siRNAs provides a simple, rapid, and cost-effective tool for new anti-HIV-1 gene therapeutics.

Animals↗
PubMed1978

Proteins of Rous-associated virus 61, an avian retrovirus: common precursor for glycoproteins gp85 and gp35 and use of pactamycin to map translational order of proteins in the gag, pol, and env genes.

Cells infected by Rous-associated virus 61 (RAV-61) contained a precursor-like protein, pr90, that was specifically precipitated by antiserum directed against envelope glycoproteins, gp85 and gp35. Tryptic peptide mapping showed that pr90 contained tryptic sequences of both gp85 and gp35. Pactamycin mapping experiments indicated that the two glycoproteins are translated from the env-mRNA in the order (5') gp85--gp35. The pactamycin mapping experiments also indicated a translational order of p10--(p27, p12)--p15 for the gag proteins; this agreement with the order previously reported from tryptic mapping studies on precursor pr76 of avian myeloblastosis virus implied that the stoichiometry of the core proteins was unchanged when virions were assembled in the presence of pactamycin. The reverse transcriptase proteins, unlike those of the env and gag genes, fell on the right side of the pactamycin map. This result is in accord with the idea that most, if not all, of the reverse transcriptase protein is translated by read-through of the gag(pol) message rather than by translation of a hypothetical pol-mRNA devoted solely to synthesis of that protein.

Avian Leukosis Virus↗
PubMed1985

Immunoglobulin G antibodies binding to a synthetic peptide deduced from the nucleotide sequence of the env gene of HTLV I in patients with leukemia and rheumatoid arthritis, HLA sensitized persons and blood donors.

A synthetic pentadecapeptide preparation, env 406-420, with an amino acid sequence deduced from the envelope glycoprotein gene of human T cell leukemia virus type I (HTLV I), was used as the antigen in an enzyme immunoassay for immunoglobulin G antibodies, exploring its usefulness for seroepidemiological purposes. The frequency of reactivity in the test groups, presented in decreasing order was: patients with rheumatoid arthritis; multitransfused nonleukemic patients; Japanese cases of adult T cell leukemia (ATL); HLA sensitized persons; Swedish cases of adult acute leukemia; and Swedish blood donors. Three American cases of ATL and 12 HTLV I seropositive monkeys did not react. In RF positive sera from patients with rheumatoid arthritis, no quantitative correlation between RF activity and anti-env 406-420 activity was seen. Anti-env 406-420 positive sera did not react or reacted only weakly with four control peptide preparations with different amino acid sequences. The experience with oligopeptide serology still is limited. Our results illustrate that unexpected cross-reactions which are hard to interpret can occur. Although absorption experiments indicated an HTLV I specific component of the reactivity, antibodies against epitopes of allo- and auto-immune specificity may also have participated.

Arthritis, Rheumatoid↗
PubMed1990

Function of the human immunodeficiency virus types 1 and 2 Rev proteins is dependent on their ability to interact with a structured region present in env gene mRNA.

The interaction of the human immunodeficiency virus type 1 (HIV-1) Rev protein with a structured region in env mRNA (the Rev-responsive element [RRE]) mediates the export of structural mRNAs from the nucleus to the cytoplasm. We demonstrated that unlike HIV-1 Rev, which functions with both the HIV-1 and HIV-2 RREs, HIV-2 Rev functions only with the HIV-2 RRE. Rev-RRE binding studies suggested that the lack of nonreciprocal complementation stems from the inability of HIV-2 Rev to interact with HIV-1 RRE RNA. Maintenance of RNA secondary structure, rather than the primary nucleotide sequence, appeared to be the major determinant for interaction of both HIV-1 and HIV-2 Rev with the HIV-2 RRE. Moreover, the binding domain of the HIV-2 RRE recognized by HIV-1 Rev was dissimilar to the binding domain of the HIV-1 RRE, in terms of both secondary structure and primary nucleotide sequence. Our results support the hypothesis that function of HIV Rev proteins and possibly the functionally similar Rex proteins encoded by the human T-cell leukemia viruses (HTLVs) HTLV-I and HTLV-II is controlled by the presence of RNA secondary structure generated within the RRE RNA.

Base Sequence↗
PubMed1984

Complete env gene deletions of three replication-defective strains of Rous sarcoma virus and a model for the origin of their genetic structures.

Replication-defective deletion mutants of Rous sarcoma virus (RSV) have been described which transform cells in culture and elaborate envelope (-) defective particles. The env deletions of two clonal variants of the Bryan strain of RSV, RSV(-)3, and RSV(-)16, and of a replication-defective variant of Schmidt-Ruppin RSV (SRN8) were analyzed by fingerprinting oligonucleotides hybridized by a molecularly cloned env DNA probe that spans from near the 3' end of pol to the 3' end of env. It was observed that all three replication-defective RSV strains are essentially complete env deletions but retain the 3' end of pol. Based on a common pol-src junction oligonucleotide that may reflect a homologous sequence repeated at both ends of env in nondefective RSV, the env deletions of RSV(-)3 and 16 appear to be isogenic. The original deletion may have involved recombination between these sequences. The absence of this oligonucleotide in SRN8 indicates that the env deletion of SRN8 has different borders and represents an independent env deletion of nondefective RSV. All three defective RSVs have the genetic structure gag-pol-src. This genetic structure is consistent with the need for a complete gag to make a particle and with the assumption that an independent src gene rather than a gag- or gag-pol-src hybrid gene functions in transformation. It is suggested that a complete pol is not necessary for, but may assist, virus particle formation.

Avian Sarcoma Viruses↗
PubMed1983

Nucleotide sequencing of an apparent proviral copy of env mRNA defines determinants of expression of the mouse mammary tumor virus env gene.

To extend our understanding of the organization and expression of the mouse mammary tumor virus genome, we determined the nucleotide sequence of large regions of a cloned mouse mammary tumor virus strain C3H provirus that appears to be a DNA copy of env mRNA. In conjunction with analysis of several additional clones of integrated and unintegrated mouse mammary tumor virus DNAs, we came to the following conclusions: (i) the mRNA for env is generated by splicing mechanisms that recognize conventional eucaryotic signals at donor and acceptor sites with a leader of at least 289 bases in length; (ii) the first of three possible initiation codons for translation of env follows the splice junction by a single nucleotide and produces a signal peptide of 98 amino acids; (iii) the amino terminal sequence of the major virion glycoprotein gp52env is confirmed by nucleotide sequencing and is encoded by a sequence beginning 584 nucleotides from the 5' end of env mRNA; (iv) the final 17 amino acids at the carboxyl terminus of the primary product of env are encoded within the long terminal repeat by the 51 bases at the 5' end of the U3 domain; and (v) bases 2 through 4 at the 5' end of the long terminal repeat constitute an initiation codon that commences an open reading frame capable of directing the synthesis of a 36-kilodalton protein.

Amino Acid Sequence↗
PubMed1989

Endogenous retroviral env genes after N-methyl-N'-nitro-N-nitrosoguanidine treatment of mouse tumor cells: stable DNA amplification and rearrangement.

Immunogenic tumor variant clones derived by N-methyl-N'-nitro-N-nitrosoguanidine treatment of Eb lymphoma cells showed structurally altered gp70 env proteins at the cell surface. To further investigate this observation we screened for complementary DNA clones encoding gp70 antigens from a lambda gt11 expression library constructed from mRNA of a mutant cell clone. Using gp70-specific antibodies, a total of 10 complementary DNA clones were identified and analyzed. DNA-sequence analysis revealed the presence of both xeno/or mink cell focus-forming-type (clones 1, 10) and endogenous ecotropic gp70 (clones 2, 3, 4). Southern blot experiments using clone 2 as a probe detected new restriction fragments and DNA amplification with high copy number in the DNAs of N-methyl-N'-nitro-N-nitrosoguanidine-treated but not in parental or 5'-azacytidine-treated control cells even after greater than 120 days in tissue culture. No alterations in the restriction fragment pattern of the genomic DNAs could be detected using H-2K-, beta-actin-, or dehydrofolate-reductase-specific gene probes. The DNA amplification of specific gp70 sequences may be related to the enhanced expression of a subset of gp70 in mutant cells that was previously found to induce syngeneic antibody production.

Animals↗
PubMed1998

[Construction of the prokaryotic expression plasmid pYNenv encoding the gp120 env gene of human immunodeficiency virus type 1 of yunnan strain].

The recombinant envelope protein of human immunodeficiency virus type 1(HIV-1) of Chinese Yunan epidemic strain was expressed in E. coli for confirming the antigenic domains of the protein. The recombinant prokaryotic expressive plasmid pYNenv was constructed by inserting the env DNA fragment which encode the gp120 of HIV-1 Yunnan strain into pBV220. The env DNA fragment was obtained by nested polymerase chain reaction with the HIV-1 infected patients peripheral blood macrophage and monocyte genomes from Yunan HIV-1 epidemic area as template. The recombinant plasmid pYNenv was confirmed by restriction enzyme analysis. The recombinant protein was expressed in E. coli DH10b by pYNenv after vibration culture at 30 degrees C for 20 hours then at 42 degrees C for 5 hours and confirmed by SDS-PAGE electrophoresis. The protein can specifically react with the serum of HIV-1 infected patient from Yunan epidemic area by Western blot assay. The result showed that the recombinant protein can be used as antigen for detection of HIV-1 membrane glycoprotein antibody as well as for the further study of the role of envelope protein in pathology.

Adult↗
PubMed2005

Molecular analysis of a 444 bp fragment of the bovine leukaemia virus gp51 env gene reveals a high frequency of non-silent point mutations and suggests the presence of two subgroups of BLV in Chile.

With the aim of achieve a better understanding of the epidemiology and distribution of bovine leukaemia virus (BLV) infection in Chile, we assessed the suitability of using DNA isolated from the leukocyte fraction of bulk milk samples to carry out PCR-RFLP and DNA sequence analysis. The env fragment of BLV was successfully amplified from 33 serologically positive bulk milk samples collected from different geographical areas in the south of Chile. Restriction analysis allowed to classify 17 isolates within the Australian subgroup and 16 within the Belgium subgroup. DNA sequence and multiple alignment analysis of eight Chilean isolates showed a significantly higher frequency of single and double nucleotide substitutions. Most of these mutations were non-silent, resulting in changes at the protein level in several important epitopes of gp51. The Chilean sequences and 59 BLV env sequences available at GenBank, were subjected to a phylogenetic analysis, resulting in four different clusters. The groups identified were not related to those previously defined by restriction analysis. Chilean isolates were included in two different clusters and were genetically not related to isolates collected from neighbouring countries. Considering our results we can conclude: (i) bulk milk samples are suitable to identify the presence of BLV allowing epidemiological and genetic studies to be conducted on large geographical areas; (ii) at least four different genetic groups of BLV were identified by phylogenetic analysis, with Chilean isolates included in two different sub clusters.

Amino Acid Sequence↗
PubMed1987

A new ELISA test for HIV antibodies using a bacterially produced viral env gene product.

Screening tests for antibodies to the human immunodeficiency virus (HIV), based on the indirect ELISA principle using viral preparations as antigen, yield a substantial number of false-positive and false-negative results. These failures are due to the lack of certain viral polypeptides or contaminating cellular polypeptides in viral preparations. Therefore, the accuracy of the screening tests should be improved by using highly purified, synthetic viral antigens. With establishment of such an ELISA antigen in mind, we examined a bacterially synthesized polypeptide [ENV(80)] that corresponds to 80 conserved amino acids of the HIV gp41 transmembrane glycoprotein. ENV(80) was expressed as a DHFR fusion protein in Escherichia coli. Results obtained by HIV ELISA and immunoprecipitation with 497 serum samples from various groups at risk of AIDS were compared with those obtained with the ENV(80) ELISA. The ENV(80) ELISA was found to be superior to the H9/HTLV-III ELISA with respect to sensitivity and specificity and is almost equivalent in accuracy to immunoprecipitation.

Acquired Immunodeficiency Syndrome↗