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Gene Review

NIb  - 

Sweet potato feathery mottle virus

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Disease relevance of NIb

  • Uridylylation of the potyvirus VPg by viral replicase NIb correlates with the nucleotide binding capacity of VPg [1].
  • The foreign sequences are cloned between the NIb replicase and capsid protein (CP) cistrons [2].
  • In a previous study, we showed that transgenic Nicotiana benthamiana NIbV3 plants, transformed with a mutated NIb coding sequence from Plum pox virus (PPV), showed a delayed, very specific, resistance phenotype, which was induced by the initial infection [3].
  • The potato A potyvirus (PVA)-encoded proteins P1, HC-Pro, P3, CI, VPg, NIaPro, NIb and coat protein (CP) were expressed as 6 x His-tagged recombinant proteins in Escherichia coli and purified to homogeneity [4].
  • The sequence is consistent with the NIb and coat protein regions of a member of the Potyviridae family of viruses [5].

High impact information on NIb

  • A genetic complementation system was developed in which tobacco etch virus (TEV) polymerase (NIb)-expressing transgenic plants or protoplasts were inoculated with NIb-defective TEV mutants [6].
  • The nucleotidylation activity of NIb is more efficient in the presence of Mn(2+) than Mg(2+) and does not require an RNA template [1].
  • These results support the hypothesis that interaction between NIa and NIb is important during TEV genome replication [7].
  • Self-interactions manifested by VPg and HCPro and an interaction between NIb and NIaPro were observed in ClYVV [8].
  • The results of this study indicate that NIaPro catalyses proteolytic cleavages preferentially in cis, and that the 6K1/CI and NIb/CP sites can also be processed in trans [9].

Chemical compound and disease context of NIb


Biological context of NIb

  • Analysis of the amino acid sequences of OMV and other potyvirus proteins showed similarities of 66% to 77% for CP, 72% to 73% for NIb and 63% to 71% for NIa proteins [11].
  • PSbMV-NY varied between experiments in its ability to induce resistance, suggesting that the sequence identity in the NIb gene is borderline for the specificity required for triggering gene silencing [12].
  • Insertions of Pro-Pro dipeptides, which were predicted to induce protein folding aberrations, at three out of four positions in NIb reduced translocation [13].
  • To understand the possible relationship between NIb nuclear localization and its function, we have studied translocation of NIb using gene fusion and plant transformation techniques [13].
  • Likewise, the region of the NIb gene sequenced shows 99% and 97% sequence identity in the deduced amino acid and the nucleotide sequences, respectively [14].

Anatomical context of NIb

  • Mutational analyses were carried out to investigate whether the nuclear inclusion protein a (NIa) C-terminal amino acids of turnip mosaic potyvirus play any roles in the cis-cleavage between NIa and NIb [15].
  • However, their ability to react against NIb was greatly altered. scFv2A fragments were transiently expressed in the cytosol of Nicotiana benthamiana and although they accumulated to low levels, inhibition-ELISA results indicated that they retained antigen-binding activity [16].
  • Furthermore, amorphous cytoplasmic inclusions induced by papaya ringspot virus contained the expected HC-Pro but additionally NIa, NIb and CI [17].

Associations of NIb with chemical compounds

  • Mutation of a highly conserved glutamic acid residue in the putative pRb-binding motif of the NIb had no detectable phenotypic effect on replication of Potato virus A (PVA) [18].
  • Only two of these differences are likely to be functionally important (His rather than Gln at position1217 in the VPg cistron; His rather than Asp at position 1776 in the NIb cistron) [19].

Other interactions of NIb

  • TEV NIs are known to contain a bifunctional genome-linked protein-viral proteinase (NIa-VPg) and RNA-dependent RNA polymerase (NIb) [20].
  • In the YTHS, P1 interacted only with CI and P3 with NIb [21].
  • To identify further these potyviruses, sequences located between the 3' end of the NIb gene and the 5' end of the CP gene were chosen to design a series of species-specific probes [22].
  • Beet mosaic virus-induced nuclear inclusions ('satellite bodies') contained in their electron-dense matrix NIa, NIb, Hc-Pro and CI and in their lacunae CP in bundles of virion-like filaments [17].

Analytical, diagnostic and therapeutic context of NIb


  1. Uridylylation of the potyvirus VPg by viral replicase NIb correlates with the nucleotide binding capacity of VPg. Puustinen, P., Mäkinen, K. J. Biol. Chem. (2004) [Pubmed]
  2. Protection of rabbits against rabbit hemorrhagic disease virus by immunization with the VP60 protein expressed in plants with a potyvirus-based vector. Fernández-Fernández, M.R., Mouriño, M., Rivera, J., Rodríguez, F., Plana-Durán, J., García, J.A. Virology (2001) [Pubmed]
  3. Suppressor activity of potyviral and cucumoviral infections in potyvirus-induced transgene silencing. Simón-Mateo, C., López-Moya, J.J., Guo, H.S., González, E., García, J.A. J. Gen. Virol. (2003) [Pubmed]
  4. VPg, coat protein and five non-structural proteins of potato A potyvirus bind RNA in a sequence-unspecific manner. Merits, A., Guo, D., Saarma, M. J. Gen. Virol. (1998) [Pubmed]
  5. Molecular evidence that the aphid-transmitted Tomato mild mottle virus belongs to the Potyviridae family but not the Potyvirus genus. Monger, W.A., Spence, N.J., Foster, G.D. Arch. Virol. (2001) [Pubmed]
  6. Complementation of tobacco etch potyvirus mutants by active RNA polymerase expressed in transgenic cells. Li, X.H., Carrington, J.C. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  7. Functional analysis of the interaction between VPg-proteinase (NIa) and RNA polymerase (NIb) of tobacco etch potyvirus, using conditional and suppressor mutants. Daròs, J.A., Schaad, M.C., Carrington, J.C. J. Virol. (1999) [Pubmed]
  8. The central and C-terminal domains of VPg of Clover yellow vein virus are important for VPg-HCPro and VPg-VPg interactions. Yambao, M.L., Masuta, C., Nakahara, K., Uyeda, I. J. Gen. Virol. (2003) [Pubmed]
  9. Proteolytic processing of potyviral proteins and polyprotein processing intermediates in insect and plant cells. Merits, A., Rajamäki, M.L., Lindholm, P., Runeberg-Roos, P., Kekarainen, T., Puustinen, P., Mäkeläinen, K., Valkonen, J.P., Saarma, M. J. Gen. Virol. (2002) [Pubmed]
  10. Nucleotide sequence of Johnsongrass mosaic potyvirus genomic RNA. Gough, K.H., Shukla, D.D. Intervirology (1993) [Pubmed]
  11. The molecular cloning and nucleotide sequencing of the 3'-terminal region of Ornithogalum mosaic virus. Burger, J.T., Brand, R.J., Rybicki, E.P. J. Gen. Virol. (1990) [Pubmed]
  12. Specificity of resistance to pea seed-borne mosaic potyvirus in transgenic peas expressing the viral replicase (Nlb) gene. Jones, A.L., Johansen, I.E., Bean, S.J., Bach, I., Maule, A.J. J. Gen. Virol. (1998) [Pubmed]
  13. Nuclear transport of tobacco etch potyviral RNA-dependent RNA polymerase is highly sensitive to sequence alterations. Li, X.H., Carrington, J.C. Virology (1993) [Pubmed]
  14. Nucleotide and deduced amino acid sequence of the 3' end of the BYMV-MI genome. Mathews, A., Dwyer, G., Wylie, S., Jones, M.G. Arch. Virol. (1995) [Pubmed]
  15. Effects of mutations in the C-terminal region of NIa protease on cis-cleavage between NIa and NIb. Kim, D.H., Han, J.S., Lew, J., Kim, S.S., Kang, B.H., Hwang, D.C., Jang, D.S., Kim, W., Song, B.D., Choi, K.Y. Virology (1998) [Pubmed]
  16. Generation and characterisation of functional recombinant antibody fragments against RNA replicase NIb from plum pox virus. Esteban, O., García, J.A., Gorris, M.T., Domínguez, E., Cambra, M. Biochem. Biophys. Res. Commun. (2003) [Pubmed]
  17. Ultrastructural localization of nonstructural and coat proteins of 19 potyviruses using antisera to bacterially expressed proteins of plum pox potyvirus. Riedel, D., Lesemann, D.E., Maiss, E. Arch. Virol. (1998) [Pubmed]
  18. Analysis of putative interactions between potyviral replication proteins and plant retinoblastoma proteins. Oruetxebarria, I., Kvarnheden, A., Valkonen, J.P. Virus Genes (2002) [Pubmed]
  19. Biological and sequence analysis of a novel European isolate of Barley mild mosaic virus that overcomes the barley rym5 resistance gene. Kanyuka, K., McGrann, G., Alhudaib, K., Hariri, D., Adams, M.J. Arch. Virol. (2004) [Pubmed]
  20. Immunocytology shows the presence of tobacco etch virus P3 protein in nuclear inclusions. Langenberg, W.G., Zhang, L. J. Struct. Biol. (1997) [Pubmed]
  21. Biochemical and genetic evidence for interactions between potato A potyvirus-encoded proteins P1 and P3 and proteins of the putative replication complex. Merits, A., Guo, D., Järvekülg, L., Saarma, M. Virology (1999) [Pubmed]
  22. A new combination of RT-PCR and reverse dot blot hybridization for rapid detection and identification of potyviruses. Hsu, Y.C., Yeh, T.J., Chang, Y.C. J. Virol. Methods (2005) [Pubmed]
  23. Characterization of petunia flower mottle virus (PetFMV), a new potyvirus infecting Petunia x hybrida. Feldhoff, A., Wetzel, T., Peters, D., Kellner, R., Krczal, G. Arch. Virol. (1998) [Pubmed]
  24. Factors affecting detection of PVY in dormant tubers by reverse transcription polymerase chain reaction and nucleic acid spot hybridization. Singh, M., Singh, R.P. J. Virol. Methods (1996) [Pubmed]
  25. A primer pair for amplifying part of the genome of all potyvirids by RT-PCR. Gibbs, A., Mackenzie, A. J. Virol. Methods (1997) [Pubmed]
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