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Biomedical subjects

A Burny

Publications and source records attributed to A Burny.

At least 91 records · Page 5Linked to original sources
PubMed1995

Wild-type p53 down-regulates transcription from oncogenic human papillomavirus promoters through the epithelial specific enhancer.

High-risk Human Papillomavirus (HPV) E6 and E7 immortalizing oncoproteins are expressed from a promoter tightly regulated by an epithelial specific enhancer. To determine if the p53 tumour suppressor protein can modulate the transcription of these genes, we performed co-transfection experiments with plasmids containing the HPV type 16 or 18 long control regions linked to the chloramphenicol acetyl transferase gene, along with p53 expression vectors. Wild-type, but not mutant, murine or human p53 expression vectors reduced the activity of reporter constructs when co-transfected into HeLa or C33 cell lines. Mutations within the HPV TATA boxes did not significantly alter the levels of p53 repression, suggesting a TATA-independent mechanism. Deletion analyses mapped the p53-responsive domain to the constitutive 230 base pair epithelial specific enhancer. In addition, the enhancer could confer p53-mediated repression when placed upstream of a heterologous promoter.

Cell Line↗
PubMed1995

Lack of LTR and ENV genetic variation during bovine leukemia virus-induced leukemogenesis.

Genetic variation of the Bovine Leukemia Virus (BLV) appears to be limited in vitro and during the latent phase of the disease. However, cells in tumors often harbor deleted proviruses that are defective for expression. In order to gain insight into the involvement of viral genetic variation during pathogenesis, the BLV LTR and the env proviral sequences were analyzed in tumor tissues. A sheep (M230) was injected with the cloned BLV provirus 344 and became persistently infected with circulating lymphocytes reaching 345,000/mm3. After 11 months, this infected sheep developed leukemia-lymphoma. DNA was extracted from peripheral blood leukocytes at the time of tumor development and the LTR and the env gene were amplified, using the polymerase chain reaction procedure, cloned, and sequenced. Twenty independent LTR and twenty env clones were analyzed. It appeared that the in vivo mutation rate in the env gene was 0.043% (eight mutations including seven transitions out of 18,300 bp). Five point mutations (all transitions) were identified in the LTR, corresponding to 0.041% modifications (four mutations out of 9740 bp). These mutation rate values (0.043 and 0.041) were close to those due to the Taq DNA polymerase errors (0.030%). Altogether, these data demonstrate the lack of genetic variation in the LTR and the env gene during this case of BLV-induced pathogenesis in vivo. They confirm that the defectiveness of some BLV proviruses in vivo, thus, is not a mandatory step in the leukemogenic process.

Animals↗
PubMed1995

Biological effect of active anti-IFN alpha immunization in HIV-infected patients.

Circulating interferon (IFN) was investigated in HIV-1 seropositive patients by measuring the IFN alpha antiviral effect in the serum. While serum of healthy seronegative individuals exhibits an antiviral effect, not due to IFNs, considered as background, serum of seropositive patients showed an additional antiviral effect due to the abnormal presence of IFN alpha. Increased titers of IFN alpha were found in the course of the HIV infection and seemed to correlate with the evolution of AIDS disease. Furthermore, patients immunized against IFN alpha had both stabilized CD4 cell count and decreased IFN alpha in their serum. HIV-1-infected patients also exhibited higher titers of natural anti-IFN antibodies than seronegative controls and the level of specific antibodies (Abs) markedly increased in immunized patients. Finally, serum from immunized patients, when compared to seronegative controls, exhibits an interferon neutralizing capacity.

Acquired Immunodeficiency Syndrome↗
PubMed1995

The YXXL signalling motifs of the bovine leukemia virus transmembrane protein are required for in vivo infection and maintenance of high viral loads.

The bovine leukemia virus (BLV) transmembrane protein (gp30) contains three YXXL motifs at its carboxyterminal end. Two of these motifs have been implicated in vitro in signal transduction pathways from the external to the intracellular compartment. In order to analyze the biological relevance of these motifs in vivo, recombinant BLV proviruses were constructed. A mutation of the tyrosine residue of the second YXXL motif completely destroyed the infectious potential of the virus in sheep. In contrast, the tyrosine of the first motif appeared to be dispensable for infectivity. However, the propagation of the recombinant virus within the animal was greatly impaired (as demonstrated by PCR and enzyme-linked immunosorbent assay). These recombinant BLVs thus exhibit an attenuated phenotype. Altogether, our data demonstrate the importance of the YXXL motifs of the BLV transmembrane protein for in vivo infection and viral propagation.

Animals↗
PubMed1995

Nucleotide sequence of the ovine P53 tumor-suppressor cDNA and its genomic organization.

A 2155 bp cDNA clone corresponding to the ovine p53 tumor suppressor gene has been isolated from a cDNA library made from the BLV-transformed YR2 cell line RNA. After the sequencing analysis, it appeared that this clone contains the entire p53 coding region (including 126 bp upstream of the ATG initiation codon). The nucleotide sequence shows a high degree of homology with the human (73%), murine (74%) and rat (66%) cDNAs. The encoded ovine p53 protein is 382 amino acids long with an apparent molecular weight of 50 kDa and shares 79% and 72% amino acid homology with the human and the mouse p53 respectively. Furthermore, the homology is not equally distributed along the molecule but is mainly located within five highly conserved regions. As its mouse and human counterparts, the ovine p53 contains a high proportion of proline residues, an acidic N-terminal domain and a basic C-terminal domain. We also report the structure of the ovine p53 gene that is similar to those already defined from other species.

Amino Acid Sequence↗
PubMed1995

Nucleotide sequence of the bovine P53 tumor-suppressor cDNA.

The bovine p53 open reading frame was cloned and characterized using a reverse transcription-polymerase chain reaction amplification (RT-PCR) method. After sequencing, it appeared that this cDNA is able to code for a 386 amino acids protein with high degree of homology with the ovine p53. Furthermore, the homology is not equally distributed along the molecule since the highest divergence is located within the exon 4. The bovine p53 shares 93% and 91% homology with the ovine p53 at the DNA and protein level respectively.

Amino Acid Sequence↗
PubMed1995

DNA polymorphism detection in Tribolium castaneum (HERBST) (Coleoptera: Tenebrionidae): potential use in stored product pest management.

Different pairs of oligonucleotide primers have used for the detection of DNA polymorphism between Tribolium castaneum strains. Amplification of a major DNA fragment and two minor was observed in all strains tested excepted for one strain from France which present only two major bands (respectively at 800 bp and 880 bp). Arbitrarily, the major band amplified from a DNA sample of the strain originating from the Philippines was choosen as a probe (sequence of 487 bp in length). The combination of this probe and restriction enzymes permitted the discrimination between strains. Our results show that RAP marker of Tribolium castaneum could be used to study its population genetics.

Animals↗
PubMed1995

Are CD4 and Fas peptide identities of gp120 relevant to the molecular basis of AIDS pathogenesis?

The release of virions from HIV-1-infected CD4 cells, although occurring readily as a result of immune activation, does not appear to be the only mechanism mediating T-cell loss in AIDS. Three other interacting HIV-1-induced immune disorders in association with viral release (the source of gp120 molecules) may also account for the constitutive T-cell depletion and functional immune suppression: 1. gp120-induced CD4(+) cell anergy, which can be reproduced in cultures of immune activated normal T-cells in the presence of gp120 or gp120 peptide containing the SLWDQ sequence identity to the CD4 molecule; 2. overproduction of IFNalpha and gamma, 3. activation-driven apoptosis of non infected T-cells. Apoptosis of T-cells could also be: 1. induced by effector components - particularly CTL and lymphotoxins produced by helper T-cells of the anti-Fas autoimmune reaction triggered by gp120 epitopes shared with the Fas/APO-1 molecule; 2. enhanced by IFN overproduction. These molecular mechanisms stress the importance in the progression to AIDS of both the viral load and HIV-induced cytokine dysregulation, including overproduction of IFNalpha, which should be considered as targets in the development of strategies for AIDS prophylaxis and immunotherapy.

Journal Article↗
PubMed1995

HIV-1 soluble antigens induced CD8+ cytotoxic T-cell responses in an immunized individual.

In an attempt to determine whether immunization of healthy HIV-1 seronegative individuals with a soluble gp160 candidate vaccine could induce an anti-HIV specific immune response, volunteers were immunized by two injections of a water-in-oil emulsion containing a mixture of gp160 antigen together with selected peptides. Following immunization, lymphocytes were collected and stimulated in vitro with autologous HIV-1-infected cells. The results showed that immunization with soluble HIV-1 envelope was able to generate CD3+ CD8+ CTLs directed to gp160 antigen. The CTL response was restricted to class I molecule HLA-A2. The CTL response was comparable to that elicited by immunization with HIV-1-envelope recombinant vaccinia virus.

AIDS Vaccines↗
PubMed1995

Gene therapy for cancer.

This review looks at various gene therapy strategies that are currently being investigated either in experimental studies or in clinical trials. These approaches attempt to either enhance the antitumor immune response of the host, express conditional toxins specifically in tumor cells, reverse the transformed phenotype of tumor cells, or protect normal tissues against the toxicities of conventional treatments.

Animals↗
PubMed1995

[Progress in vaccination against AIDS].

Two vaccination trials against AIDS viruses are reported. The first trial was a prophylactic vaccination carried out in the pig-tailed macaque (Macacca nemestrina) against simian immunodeficiency virus (SIV) variant PBj14. The immunogen was a Semliki forest virus (SFV) recombinant expressing SFV - PBj14 envelope protein. Vaccination did not prevent infection but protected the animals against the disease (a fulminant form of AIDS that kills the animal within 12-15 days). The second trial was a therapeutic vaccination carried out with HIV-I-infected hemophilic patients. The immunogen was a toxoïd of alpha interferons. (A toxoïd of alpha interferons is an inactivated and immunogenic preparation of alpha interferons). Vaccination induced the production of neutralizing anti alpha interferon antibody. As a result, circulating alpha interferon concentrations were drastically lowered and the clinical status of patients significantly improved.

AIDS Vaccines↗
PubMed1994

Structure of the gene encoding pig phosphoglucose isomerase.

Genomic clones encoding pig phosphoglucose isomerase (PGI) have been isolated and partially sequenced. The gene (Pgi) contains 18 exons, 17 introns and spans about 32 kb. This structure is partially conserved between plant and animal. A major transcription start point (tsp) has been identified 74 nucleotides (nt) upstream from the AUG. The nt sequence around the tsp is very G+C rich; a 5'-ATAAA sequence, as well as four putative Sp1-binding sites, are present. In the 3'-flanking region, an AATAAA signal has been identified. Extending from the 5'-flanking region to the first intron, a 0.6-kb CpG island has been identified. The Pgi structural gene contains several DNA repetitive elements in its non-coding regions.

Alternative Splicing↗
PubMed1994

Attenuation of bovine leukemia virus by deletion of R3 and G4 open reading frames.

Complex oncoviruses contain, in addition to the classical retroviral genes (gag, pol, and env), a region (X) located between the envelope sequences and the 3' long terminal repeat. The X region contains two genes, tax and rex, whose protein products are involved in transcriptional and posttranscriptional regulation of viral expression. In addition to these activators, the bovine leukemia virus (BLV) and the human T-cell leukemia virus (HTLV) contain alternative open reading frames (R3 and G4 for BLV; p30, p13, and p12 for HTLV). As a virus/animal model for HTLV-induced leukemogenesis, BLV provirus can be injected intradermally into sheep, where it induced B-lymphocyte transformation. Deletion of the R3 and G4 sequences from an infectious and tumorigenic BLV provirus greatly impaired the in vivo propagation of the viruses as demonstrated by DNA polymerase chain reaction, RNA blots, structural-protein ELISA, and immunofluorescence analysis. Our results show that the alternative open reading frames are required for maintaining high virus loads during the course of persistent infection in vivo. Thus, R3 and G4 are candidates for antiviral drug development. Furthermore, viruses with a deletion in these sequences should be tested as live attenuated vaccines.

Animals↗
PubMed1994

Identification of functional sites on bovine leukemia virus envelope glycoproteins using structural and immunological data.

Sequence analysis using the sensitive hydrophobic cluster analysis method shows that the bovine leukemia virus envelope glycoproteins conserve the general organization of the influenza hemagglutinin into a 'stem', containing the external part of the transmembrane glycoprotein and the N-terminal and C-terminal parts of the external glycoprotein, and a 'head', containing only external glycoprotein residues. However, our analysis suggests, for the first time, that the bovine leukemia virus envelope head will not adopt the typical 'jelly-roll' fold of the influenza A hemagglutinin head, but most likely folds into another type of 'Greek-key' structure corresponding to the overall topology of constant immunoglobulin domains. We constructed a three-dimensional model for the bovine leukemia virus envelope head by homology modeling using the crystal structure of the human histocompatibility antigen HLA-A2 alpha 3 domain. Furthermore, we propose a general model for the oligomeric organization of this head, based on the hemagglutinin trimer. The proposed structural organization of bovine leukemia virus external glycoprotein is further supported by antipeptide and monoclonal antibody reactivities. Our modeling study suggests that the loops of the two neutralizing peptides located in the head are adjacent at the top of the domain and define a potential interaction site of the external glycoprotein with its cellular receptor. This site is topologically similar to the binding site of hemagglutinin with its cellular receptor, sialic acid. The other neutralizing peptides are located within a small domain linking the head to the stem. These data are of interest for defining other oncoviral glycoproteins heads and receptor-binding sites.

Amino Acid Sequence↗
PubMed1994

Structural similarities between chaperone molecules of the HSP60 and HSP70 families deduced from hydrophobic cluster analysis.

In this study, the conservation of strong structural landmarks between all the members of two chaperone families (HSP60 and HSP70) was deduced from their sequences by hydrophobic cluster analysis. On this basis, we propose that the ATP-binding environment is maintained by a similar fold in both protein families. The observed similarities extend throughout the proteins, including both the ATPase domain and the C-terminal substrate-binding domain.

Adenosine Triphosphatases↗
PubMed1994

Common prevalence of alanine and glycine in mobile reactive centre loops of serpins and viral fusion peptides: do prions possess a fusion peptide?

Serpin reactive centre loops and fusion peptides released by proteolytic cleavage are particularly mobile. Their amino acid compositions reveal a common and unusual abundance of alanine, accompanied by high levels of glycine. These two small residues, which are not simultaneously abundant in stable helices (standard or transmembrane), probably play an important role in mobility. Threonine and valine (also relatively small amino acids) are also abundant in these two kinds of peptides. Moreover, the known 3D structures of an uncleaved serpin reactive centre and a fusion peptide are strikingly similar. Such sequences possess many small residues and are found in several signal peptides and in PrP, a protein associated with spongiform encephalopathies and resembling virus envelope proteins. These properties may be related to the infection mechanisms of these diseases.

Alanine↗