Isabelle Jupin

Publications (32) View all

• Chapter: Family Tymoviridae

  Dreher T.W, M.C. Edwards, A-L. Haenni, R.W. Hammond, I. Jupin, R. Koenig, S. Sabanadzovic, G.P. Martelli
  01/2012: pages 913-921; , ISBN: 978-0-12-384684-6
• Article: Detection and subcellular localization of the turnip yellow mosaic virus 66K replication protein in infected cells.

  D Prod'homme, S Le Panse, G Drugeon, I Jupin
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  ABSTRACT: Turnip yellow mosaic virus (TYMV) encodes a 206-kDa (206K) polyprotein with domains of methyltransferase, proteinase, NTPase/helicase, and RNA-dependent RNA polymerase (RdRp). In vitro, the 206K protein has been shown to undergo proteolytic processing, giving rise to the synthesis of 140-kDa (140K) and 66-kDa (66K) proteins, the latter comprising the RdRp protein domain. Antibodies were raised against the 66K protein and were used to detect the corresponding viral protein in infected cells; both leaf tissues and protoplasts were examined. The antiserum specifically recognized a protein of approximately 66 kDa, indicating that the cleavage observed in vitro is also functional in vivo. The 66K protein accumulates transiently during protoplast infection and localizes to cellular membrane fractions. Indirect immunofluorescence assays and electron microscopy of immunogold-decorated ultrathin sections of infected leaf tissue using anti-66K-specific antibody revealed labeling of membrane vesicles located at the chloroplast envelope.
  Virology 04/2001; 281(1):88-101. · 3.35 Impact Factor
• Article: Evidence for phosphorylation and ubiquitinylation of the turnip yellow mosaic virus RNA-dependent RNA polymerase domain expressed in a baculovirus-insect cell system.

  F Héricourt, S Blanc, V Redeker, I Jupin
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  ABSTRACT: All RNA viruses known to date encode an RNA-dependent RNA polymerase (RdRp) that is required for replication of the viral genome. We have expressed and purified the turnip yellow mosaic virus (TYMV) RdRp in insect cells using a recombinant baculovirus, either in its native form, or fused to an hexa-histidine tag. Phosphorylation of the protein was demonstrated by labelling experiments in vivo, as well as phosphatase treatment of the purified protein in vitro. Phospho amino acid analysis and immunoblotting experiments identified serine and threonine residues as being the subject of phosphorylation. Peptide mass mapping using MS analysis of a protein digest revealed that phosphorylation sites are localized within a putative PEST sequence [a sequence rich in proline (P), glutamic acid (E), serine (S) and threonine (T) residues] in the N-terminal region of the protein. Using monoclonal antibodies specific for ubiquitin conjugates, we were able to demonstrate that the TYMV RdRp is conjugated to ubiquitin molecules when expressed in insect cells. These observations suggest that the TYMV RdRp may be processed selectively by the ubiquitin/proteasome degradation system upon phosphorylation of the PEST sequence.
  Biochemical Journal 08/2000; 349(Pt 2):417-25. · 4.90 Impact Factor
• Article: Molecular cloning and characterization of the Arabidopsis thaliana alpha-subunit of elongation factor 1B.

  F Héricourt, I Jupin
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  ABSTRACT: Using a PCR-based approach, we have isolated two Arabidopsis thaliana cDNA clones (alpha1 and alpha2) encoding the alpha-subunit of translation elongation factor 1B (eEF1Balpha). They encode open reading frames of 228 and 224 amino acids respectively, with extensive homology to eEF1Balpha subunits from different organisms, particularly in the C-terminal half of the protein. They both lack a conserved phosphorylation site that has been implicated in regulating nucleotide exchange activity. Using a plasmid shuffling experiment, we demonstrated that both alpha1 and alpha2 clones are able to complement a mutant yeast strain deficient for the eEF1Balpha subunit. This provides evidence that Arabidopsis encodes at least two functional isoforms of this subunit, termed eEF1Balpha1 and eEF1Balpha2. A third cDNA clone was isolated that appeared to result from an alternative splicing event of the eEF1Balpha1 gene.
  FEBS Letters 01/2000; 464(3):148-52. · 3.54 Impact Factor
• Article: Genetic analysis of the monopartite tomato yellow leaf curl geminivirus: roles of V1, V2, and C2 ORFs in viral pathogenesis.

  L Wartig, A Kheyr-Pour, E Noris, F De Kouchkovsky, F Jouanneau, B Gronenborn, I Jupin
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  ABSTRACT: Tomato yellow leaf curl virus (TYLCV) is a whitefly-transmitted geminivirus with a monopartite genome. We have investigated the functions of the V1, V2, and C2 ORFs by mutational analysis. We analyzed the ability of TYLCV mutants containing disrupted ORFs V1, V2, or C2 to replicate, spread, and cause symptoms in Nicotiana benthamiana and tomato plants. All the mutants retained the capability of autonomous replication in protoplast-derived cells of tomato and leaf discs of N. benthamiana, although both V1 and V2 gene products appeared to play a role in the accumulation of viral single-stranded DNA. In contrast, none of the mutants was able to systemically infect tomato plants, demonstrating that the V1, V2, and C2 gene products are all required for a successful infection process in this host. The effect of the mutation in ORF C2 appeared to be host-specific, since N. benthamiana plants were systemically infected, although symptom development was attenuated.
  Virology 03/1997; 228(2):132-40. · 3.35 Impact Factor