Recombinant Human Nuclear cap-binding protein subunit 1 (NCBP1)

Function

Component of the cap-binding complex (CBC), which binds cotranscriptionally to the 5'-cap of pre-mRNAs and is involved in various processes such as pre-mRNA splicing, translation regulation, nonsense-mediated mRNA decay, RNA-mediated gene silencing (RNAi) by microRNAs (miRNAs) and mRNA export. The CBC complex is involved in mRNA export from the nucleus via its interaction with ALYREF/THOC4/ALY, leading to the recruitment of the mRNA export machinery to the 5'-end of mRNA and to mRNA export in a 5' to 3' direction through the nuclear pore. The CBC complex is also involved in mediating U snRNA and intronless mRNAs export from the nucleus. The CBC complex is essential for a pioneer round of mRNA translation, before steady state translation when the CBC complex is replaced by cytoplasmic cap-binding protein eIF4E. The pioneer round of mRNA translation mediated by the CBC complex plays a central role in nonsense-mediated mRNA decay (NMD), NMD only taking place in mRNAs bound to the CBC complex, but not on eIF4E-bound mRNAs. The CBC complex enhances NMD in mRNAs containing at least one exon-junction complex (EJC) via its interaction with UPF1, promoting the interaction between UPF1 and UPF2. The CBC complex is also involved in 'failsafe' NMD, which is independent of the EJC complex, while it does not participate in Staufen-mediated mRNA decay (SMD). During cell proliferation, the CBC complex is also involved in microRNAs (miRNAs) biogenesis via its interaction with SRRT/ARS2 and is required for miRNA-mediated RNA interference. The CBC complex also acts as a negative regulator of PARN, thereby acting as an inhibitor of mRNA deadenylation. In the CBC complex, NCBP1/CBP80 does not bind directly capped RNAs (m7GpppG-capped RNA) but is required to stabilize the movement of the N-terminal loop of NCBP2/CBP20 and lock the CBC into a high affinity cap-binding state with the cap structure. Associates with NCBP3 to form an alternative cap-binding complex (CBC) which plays a key role in mRNA export and is particularly important in cellular stress situations such as virus infections. The conventional CBC with NCBP2 binds both small nuclear RNA (snRNA) and messenger (mRNA) and is involved in their export from the nucleus whereas the alternative CBC with NCBP3 does not bind snRNA and associates only with mRNA thereby playing a role only in mRNA export. NCBP1/CBP80 is required for cell growth and viability (PubMed:26382858)

Subcellular Location

Nucleus; Cytoplasm

Subunit

Component of the nuclear cap-binding complex (CBC), a heterodimer composed of NCBP1/CBP80 and NCBP2/CBP20 that interacts with m7GpppG-capped RNA. Found in a U snRNA export complex containing PHAX/RNUXA, NCBP1/CBP80, NCBP2/CBP20, RAN, XPO1 and m7G-capped RNA. Identified in a IGF2BP1-dependent mRNP granule complex containing untranslated mRNAs. Interacts with PHAX/RNUXA, SRRT/ARS2, EIF4G2, IGF2BP1, HNRNPF, HNRNPH1, KIAA0427/CTIF, PARN, DROSHA, UPF1 and ALYREF/THOC4. May interact with EIF4G1; the interaction is however controversial since it is reported by PubMed:11340157, PubMed:15059963 and PubMed:15361857, but is not observed by PubMed:19648179. The large PER complex involved in the repression of transcriptional termination is composed of at least PER2, CDK9, DDX5, DHX9, NCBP1/CBP80 and POLR2A. Component of an alternative nuclear cap-binding complex (CBC) composed of NCBP1/CBP80 and NCBP3 (PubMed:26382858). Interacts with METTL3 (PubMed:27117702). Interacts with ZFC3H1 in a RNase-insensitive manner (PubMed:27871484). Interacts with MTREX (PubMed:30842217). Interacts with DHX34; the interaction is RNA-dependent (PubMed:25220460). Interacts with KPNA3 (PubMed:34564892)

• Izaurralde E. et al. A nuclear cap binding protein complex involved in pre-mRNA splicing. — Cell (1994)
• Kataoka N. et al. Cloning of a complementary DNA encoding an 80 kilodalton nuclear cap binding protein. — Nucleic Acids Res. (1994)
• Ota T. et al. Complete sequencing and characterization of 21,243 full-length human cDNAs. — Nat. Genet. (2004)
• Totoki Y. et al. PubMed: CI-6FM9UGIHPC7GG (MAR-)
• Humphray S.J. et al. DNA sequence and analysis of human chromosome 9. — Nature (2004)
• The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). — Genome Res. (2004)
• Izaurralde E. et al. A cap-binding protein complex mediating U snRNA export. — Nature (1995)
• Gamberi C. et al. Interaction between the human nuclear cap-binding protein complex and hnRNP F. — Mol. Cell. Biol. (1997)