Component of the cap-binding complex (CBC), which bindscotranscriptionally to the 5'-cap of pre-mRNAs and is involved invarious processes such as pre-mRNA splicing, translation regulation, nonsense-mediated mRNA decay, RNA-mediated gene silencing (RNAi) bymicroRNAs (miRNAs) and mRNA export. The CBC complex is involved in mRNAexport from the nucleus via its interaction with ALYREF/THOC4/ALY, leading to the recruitment of the mRNA export machinery to the 5'-endof mRNA and to mRNA export in a 5' to 3' direction through the nuclearpore. The CBC complex is also involved in mediating U snRNA andintronless mRNAs export from the nucleus. The CBC complex is essentialfor a pioneer round of mRNA translation, before steady statetranslation when the CBC complex is replaced by cytoplasmic cap-bindingprotein eIF4E. The pioneer round of mRNA translation mediated by theCBC complex plays a central role in nonsense-mediated mRNA decay (NMD), NMD only taking place in mRNAs bound to the CBC complex, but not oneIF4E-bound mRNAs. The CBC complex enhances NMD in mRNAs containing atleast one exon-junction complex (EJC) via its interaction with UPF1, promoting the interaction between UPF1 and UPF2. The CBC complex isalso involved in 'failsafe' NMD, which is independent of the EJCcomplex, while it does not participate in Staufen-mediated mRNA decay (SMD). During cell proliferation, the CBC complex is also involved inmicroRNAs (miRNAs) biogenesis via its interaction with SRRT/ARS2 and isrequired for miRNA-mediated RNA interference. The CBC complex also actsas a negative regulator of PARN, thereby acting as an inhibitor of mRNAdeadenylation. In the CBC complex, NCBP1/CBP80 does not bind directlycapped RNAs (m7GpppG-capped RNA) but is required to stabilize themovement of the N-terminal loop of NCBP2/CBP20 and lock the CBC into ahigh affinity cap-binding state with the cap structure. Associates withNCBP3 to form an alternative cap-binding complex (CBC) which plays akey role in mRNA export and is particularly important in cellularstress situations such as virus infections. The conventional CBC withNCBP2 binds both small nuclear RNA (snRNA) and messenger (mRNA) and isinvolved in their export from the nucleus whereas the alternative CBCwith NCBP3 does not bind snRNA and associates only with mRNA therebyplaying a role only in mRNA export. NCBP1/CBP80 is required for cellgrowth and viability. [1-14]

MSRRRHSDENDGGQPHKRRKTSDANETEDHLESLICKVGEKSACSLESNLEGLAGVLEADLPNYKSKILRLLCTVARLLPEKLTIYTTLVGLLNARNYNFGGEFVEAMIRQLKESLKANNYNEAVYLVRFLSDLVNCHVIAAPSMVAMFENFVSVTQEEDVPQVRRDWYVYAFLSSLPWVGKELYEKKDAEMDRIFANTESYLKRRQKTHVPMLQVWTADKPHPQEEYLDCLWAQIQKLKKDRWQERHILRPYLAFDSILCEALQHNLPPFTPPPHTEDSVYPMPRVIFRMFDYTDDPEGPVMPGSHSVERFVIEENLHCIIKSHWKERKTCAAQLVSYPGKNKIPLNYHIVEVIFAELFQLPAPPHIDVMYTTLLIELCKLQPGSLPQVLAQATEMLYMRLDTMNTTCVDRFINWFSHHLSNFQFRWSWEDWSDCLSQDPESPKPKFVREVLEKCMRLSYHQRILDIVPPTFSALCPANPTCIYKYGDESSNSLPGHSVALCLAVAFKSKATNDEIFSILKDVPNPNQDDDDDEGFSFNPLKIEVFVQTLLHLAAKSFSHSFSALAKFHEVFKTLAESDEGKLHVLRVMFEVWRNHPQMIAVLVDKMIRTQIVDCAAVANWIFSSELSRDFTRLFVWEILHSTIRKMNKHVLKIQKELEEAKEKLARQHKRRSDDDDRSSDRKDGVLEEQIERLQEKVESAQSEQKNLFLVIFQRFIMILTEHLVRCETDGTSVLTPWYKNCIERLQQIFLQHHQIIQQYMVTLENLLFTAELDPHILAVFQQFCALQA