Nuclear cap-binding protein subunit 2 (NCBP2, also known as CBC2 and CBP20) forms the CBC complex with the nuclear cap-binding protein subunit 1 (). The CBC complex binds co-transcriptionally to the 5' cap of pre-mRNAs and is involved in maturation, export and degradation of nuclear mRNAs [, , , ]. In humans, the CBC complex is also involved in mediating U snRNA and intronless mRNAs export from the nucleus and plays a central role in nonsense-mediated mRNA decay (NMD) []. During cell proliferation, the CBC complex is involved in microRNAs (miRNAs) biogenesis via its interaction with SRRT/ARS2, thereby being required for miRNA-mediated RNA interference [].
The cap-binding complex (CBC) consisting of NCBP2 and its adaptor NCBP1 is believed to bind all capped RNA and to be necessary for its processing and intracellular localisation. Nuclear cap-binding protein subunit 3 (NCBP3), together with NCBP1, forms an alternative CBC in higher eukaryotes. NCBP3 binds mRNA, associates with components of the mRNA processing machinery and contributes to poly(A) RNA export [].
