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Gene Review

NCBP1  -  nuclear cap binding protein subunit 1, 80kDa

Homo sapiens

Synonyms: 80 kDa nuclear cap-binding protein, CBP80, NCBP, NCBP 80 kDa subunit, Nuclear cap-binding protein subunit 1, ...
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High impact information on NCBP1

  • Evidence for a pioneer round of mRNA translation: mRNAs subject to nonsense-mediated decay in mammalian cells are bound by CBP80 and CBP20 [1].
  • Consistent with the dependence of NMD on translation, the NMD of CBP80-bound mRNA is blocked by cycloheximide or suppressor tRNA [1].
  • Polysome profiles indicate that CBP80-bound mRNAs are translated less efficiently than their eIF4E-bound counterparts [2].
  • hnRNP F was identified in a screen for proteins that interact with human CBP80 and CBP20, the components of the nuclear cap-binding complex (CBC) [3].
  • The CBC-mediated inhibition of PARN was cap-independent, and in keeping with this, the CBP80 subunit alone inhibited PARN [4].

Biological context of NCBP1

  • Here, we provide evidence that CBP80 augments the efficiency of NMD but not of Staufen1 (Stau1)-mediated mRNA decay (SMD) [5].
  • In vertebrates, a nuclear cap-binding complex (CBC) formed by two cap- binding proteins, CBP20 and CBP80, is involved in several steps of RNA metabolism, including pre-mRNA splicing and nuclear export of some RNA polymerase II-transcribed U snRNAs [6].
  • S6 kinase may directly target the CBC in vivo as it can phosphorylate the 80-kDa subunit of the CBC, CBP80, at residues that are subject to a growth factor-dependent and rapamycin-sensitive phosphorylation in vivo [7].
  • We have previously identified and purified an 80kD Nuclear Cap Binding Protein (NCBP) from a HeLa cell nuclear extract, which could possibly mediate these nuclear activities [8].
  • Transfection experiments demonstrated that the epitope-tagged NCBP, transiently expressed in HeLa cells, was localized exclusively in the nucleoplasm [8].

Anatomical context of NCBP1

  • As a candidate for the factor involved in these nuclear events we have previously purified an 80 kDa nuclear cap binding protein (NCBP) from a HeLa cell nuclear extract and isolated its full-length cDNA [9].
  • The soluble stimuli formlymethionyl-leucyl-phenylalanine and the low-molecular-weight complement fragment C5a both promote the dose-dependent release of NCBP from cytochalasin B-treated neutrophils in vitro [10].

Associations of NCBP1 with chemical compounds

  • The CBC represents a 20- and 80-kDa heterodimer (the subunits independently referred to as CBP20 and CBP80, respectively) that binds the 7-methylguanosine cap on RNAs transcribed by RNA polymerase II [11].
  • A complex with a small N-terminal deletion in CBP80 was crystallized in space group C2 with one complex per asymmetric unit [12].
  • The extracellular discharge of NCBP induced by higher secretagogue is inhibited by prior exposure of neutrophils to the corticosteroids hydrocortisone and methylprednisolone and the nonsteroidal antiinflammatory agents indomethacin and ibuprofen [10].

Physical interactions of NCBP1

  • CBP80 stabilizes the movement of the N-terminal loop of CBP20 and locks the CBC into a high affinity cap-binding state [13].
  • We propose a model in which eIF4G serves to connect CBP80/20 with other initiation factors during the pioneer round of translation [14].

Other interactions of NCBP1

  • The cap-bound conformation of CBP20 is stabilized by an intricate network of interactions both to the ligand and within the subunit, as well as new interactions of the CBP20 N-terminal tail with the large subunit CBP80 [15].
  • Here, we present evidence that eIF4G and the large subunit of the nuclear cap-binding complex, CBP80, share a common origin and domain structure [16].
  • We showed that CBC, via its 80-kDa subunit (CBP80), inhibited PARN, suggesting that CBC can regulate mRNA deadenylation [4].

Analytical, diagnostic and therapeutic context of NCBP1

  • Here, the engineering and crystallization of two variant CBCs with deletions in CBP80 which do not affect function are described [12].


  1. Evidence for a pioneer round of mRNA translation: mRNAs subject to nonsense-mediated decay in mammalian cells are bound by CBP80 and CBP20. Ishigaki, Y., Li, X., Serin, G., Maquat, L.E. Cell (2001) [Pubmed]
  2. The pioneer translation initiation complex is functionally distinct from but structurally overlaps with the steady-state translation initiation complex. Chiu, S.Y., Lejeune, F., Ranganathan, A.C., Maquat, L.E. Genes Dev. (2004) [Pubmed]
  3. Interaction between the human nuclear cap-binding protein complex and hnRNP F. Gamberi, C., Izaurralde, E., Beisel, C., Mattaj, I.W. Mol. Cell. Biol. (1997) [Pubmed]
  4. Inhibition of mRNA deadenylation by the nuclear cap binding complex (CBC). Balatsos, N.A., Nilsson, P., Mazza, C., Cusack, S., Virtanen, A. J. Biol. Chem. (2006) [Pubmed]
  5. CBP80 promotes interaction of Upf1 with Upf2 during nonsense-mediated mRNA decay in mammalian cells. Hosoda, N., Kim, Y.K., Lejeune, F., Maquat, L.E. Nat. Struct. Mol. Biol. (2005) [Pubmed]
  6. A nuclear cap-binding complex binds Balbiani ring pre-mRNA cotranscriptionally and accompanies the ribonucleoprotein particle during nuclear export. Visa, N., Izaurralde, E., Ferreira, J., Daneholt, B., Mattaj, I.W. J. Cell Biol. (1996) [Pubmed]
  7. Cdc42 stimulates RNA splicing via the S6 kinase and a novel S6 kinase target, the nuclear cap-binding complex. Wilson, K.F., Wu, W.J., Cerione, R.A. J. Biol. Chem. (2000) [Pubmed]
  8. Cloning of a complementary DNA encoding an 80 kilodalton nuclear cap binding protein. Kataoka, N., Ohno, M., Kangawa, K., Tokoro, Y., Shimura, Y. Nucleic Acids Res. (1994) [Pubmed]
  9. Identification of the factors that interact with NCBP, an 80 kDa nuclear cap binding protein. Kataoka, N., Ohno, M., Moda, I., Shimura, Y. Nucleic Acids Res. (1995) [Pubmed]
  10. Inhibition of human neutrophil secondary granule discharge by antiinflammatory agents. Davies, J., Sheppard, K., Fletcher, J. Inflammation (1984) [Pubmed]
  11. The nuclear cap-binding complex is a novel target of growth factor receptor-coupled signal transduction. Wilson, K.F., Fortes, P., Singh, U.S., Ohno, M., Mattaj, I.W., Cerione, R.A. J. Biol. Chem. (1999) [Pubmed]
  12. Co-crystallization of the human nuclear cap-binding complex with a m7GpppG cap analogue using protein engineering. Mazza, C., Segref, A., Mattaj, I.W., Cusack, S. Acta Crystallogr. D Biol. Crystallogr. (2002) [Pubmed]
  13. Structural basis of m7GpppG binding to the nuclear cap-binding protein complex. Calero, G., Wilson, K.F., Ly, T., Rios-Steiner, J.L., Clardy, J.C., Cerione, R.A. Nat. Struct. Biol. (2002) [Pubmed]
  14. eIF4G is required for the pioneer round of translation in mammalian cells. Lejeune, F., Ranganathan, A.C., Maquat, L.E. Nat. Struct. Mol. Biol. (2004) [Pubmed]
  15. Large-scale induced fit recognition of an m(7)GpppG cap analogue by the human nuclear cap-binding complex. Mazza, C., Segref, A., Mattaj, I.W., Cusack, S. EMBO J. (2002) [Pubmed]
  16. eIF4G and CBP80 share a common origin and similar domain organization: implications for the structure and function of eIF4G. Marintchev, A., Wagner, G. Biochemistry (2005) [Pubmed]
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