Oncoviral bovine leukemia virus G4 and human T-cell leukemia virus type 1 p13(II) accessory proteins interact with farnesyl pyrophosphate synthetase

in Journal of Virology (2002), 76(3), 1400-1414

G4 and p13(II) are accessory proteins encoded by the X region of bovine leukemia virus and human T-cell leukemia virus type 1 (HTLV-1), respectively. Disruption of the G4 and p13(II) open reading frames ... [more ▼]

G4 and p13(II) are accessory proteins encoded by the X region of bovine leukemia virus and human T-cell leukemia virus type 1 (HTLV-1), respectively. Disruption of the G4 and p13(II) open reading frames interferes with viral spread in animal model systems, indicating that the corresponding proteins play a key role in viral replication. In addition, G4 is oncogenic in primary cell cultures and is absolutely required for efficient onset of leukemogenesis in sheep. To gain insight into the function of these proteins, we utilized the yeast two-hybrid system to identify protein partners of G4. Results revealed that G4 interacts with farnesyl pyrophosphate synthetase (FPPS), a protein involved in the mevalonate/squalene pathway and in synthesis of FPP, a substrate required for prenylation of Ras. The specificity of the interaction was verified by glutathione S-transferase (GST) pull-down assays and by coimmunoprecipitation experiments. Furthermore, confocal microscopy showed that the subcellular localization of G4 was profoundly affected by FPPS. The G4 protein itself was not prenylated, at least in rabbit reticulocyte lysate-based assays. The domain of G4 required for binding to FPPS was restricted to an amphipathic alpha-helix rich in arginine residues. Subtle mutation of this alpha-helix abrogated G4 oncogenic potential in vitro, providing a biological relevance for FPPS-G4 complex formation in cells. Finally, HTLV-1 p13(II) was also found to specifically interact with FPPS (in yeast as well as in GST pull-down assays) and to colocalize with G4 in mitochondria, suggesting a functional analogy between these oncoviral accessory proteins. Identification of FPPS as a molecular partner for p13(II) and G4 accessory proteins opens retrovirus-induced leukemia. [less ▲]

Effect of the msb3 msb4 double mutation on the intracellular pool of purine nucleotides in the yeast Saccharomyces cerevisiae: application to the study of the biological activity of the oncogenic human protein oncTre2210p.

Poster (2001, August)

Effect of the msb3 msb4 double mutation on the intracellular pool of purine nucleotides in the yeast Saccharomyces cerevisiae: application to the study of the biological activity of the oncogenic human protein oncTre210p.

Poster (2001, May)

Biotechnology in animal husbandry

Book published by Cluwer Academic Publishers (2001)

Discordance between bovine leukemia virus tax immortalization in vitro and oncogenicity in vivo.

in Journal of Virology (2000), 74(21), 9895-902

Bovine leukemia virus (BLV) Tax protein, a transcriptional activator of viral expression, is essential for viral replication in vivo. Tax is believed to be involved in leukemogenesis because of its second ... [more ▼]

Bovine leukemia virus (BLV) Tax protein, a transcriptional activator of viral expression, is essential for viral replication in vivo. Tax is believed to be involved in leukemogenesis because of its second function, immortalization of primary cells in vitro. These activities of Tax can be dissociated on the basis of point mutations within specific regions of the protein. For example, mutation of the phosphorylation sites at serines 106 and 293 abrogates immortalization potential in vitro but maintains transcriptional activity. This type of mutant is thus particularly useful for unraveling the role of Tax immortalization activity during leukemogenesis independently of viral replication. In this report, we describe the biological properties of BLV recombinant proviruses mutated in the Tax phosphorylation sites (BLVTax106+293). Titration of the proviral loads by semiquantitative PCR revealed that the BLV mutants propagated at wild-type levels in vivo. Furthermore, two animals (sheep 480 and 296) infected with BLVTax106+293 developed leukemia or lymphosarcoma after 16 and 36 months, respectively. These periods of time are within the normal range of latencies preceding the onset of pathogenesis induced by wild-type viruses. The phenotype of the mutant-infected cells was characteristic of a B lymphocyte (immunoglobulin M positive) expressing CD11b and CD5 (except at the final stage for the latter marker), a pattern that is typical of wild-type virus-infected target cells. Interestingly, the transformed B lymphocytes from sheep 480 also coexpressed the CD8 marker, a phenotype rarely observed in tumor biopsies from chronic lymphocytic leukemia patients. Finally, direct sequencing of the tax gene demonstrated that the leukemic cells did not harbor revertant proviruses. We conclude that viruses expressing a Tax mutant unable to transform primary cells in culture are still pathogenic in the sheep animal model. Our data thus provide a clear example of the discordant conclusions that can be drawn from in vitro immortalization assays and in vivo experiments. These observations could be of interest for other systems, such as the related human T-cell leukemia virus type 1, which currently lack animal models allowing the study of the leukemogenic process. [less ▲]

Implication de la protéine transmembranaire d’enveloppe du virus de la leucémie bovine dans la fusion cellulaire et l’infectivité virale.

in Séminaire de la Recherche Télévie (1999, March 16)

Growth hormone binding protein (GHBP) during lactation in cows

in Archivio Veterinario Italiano (1998), 48

Insulin-like growth factor-I (IGF-i), IGF-binding proteininding proteins synthesis, and thyroid status are affected by dexamethasone esters treatment in finishing calves.

Poster (1998)

Sélection assistée par marqueurs génétiques en spéculation laitière.

in 3° Carrefour des Productions Animales (1998)

Pit-1 gene HinfI RFLP and growth traits in double-muscled Belgian Blue cattle

in Journal of Animal Science (1997), 75(1), 146