NCBP2
Description
The NCBP2 (nuclear cap binding protein subunit 2) is a protein-coding gene located on chromosome 3.
NCBP2, also known as CBP20, is a subunit of the nuclear cap-binding complex (CBC). The CBC binds to the 5' cap of pre-mRNAs during transcription and plays a critical role in various processes, including pre-mRNA splicing, translation regulation, nonsense-mediated mRNA decay (NMD), RNA interference (RNAi) by microRNAs (miRNAs), and mRNA export. The CBC mediates mRNA export from the nucleus by interacting with ALYREF/THOC4/ALY, recruiting the export machinery to the 5' end of mRNA, and facilitating export in a 5' to 3' direction through the nuclear pore. It also mediates the export of U snRNA and intronless mRNAs. The CBC is essential for the initial round of mRNA translation, known as the pioneer round, before the steady-state translation when the CBC is replaced by the cytoplasmic cap-binding protein eIF4E. This pioneer round is crucial for NMD, which only occurs in CBC-bound mRNAs. The CBC enhances NMD in mRNAs containing exon-junction complexes (EJCs) by interacting with UPF1 and promoting the interaction between UPF1 and UPF2. It also participates in 'failsafe' NMD, which is independent of the EJC complex, but it does not play a role in Staufen-mediated mRNA decay (SMD). During cell proliferation, the CBC is involved in miRNA biogenesis through its interaction with SRRT/ARS2, a crucial component of miRNA-mediated RNA interference. The CBC also acts as a negative regulator of PARN, inhibiting mRNA deadenylation. Within the CBC, NCBP2/CBP20 recognizes and binds capped RNAs (m7GpppG-capped RNA), but it requires NCBP1/CBP80 to stabilize its N-terminal loop and lock the CBC into a high-affinity cap-binding state. The CBC, with NCBP2, binds both small nuclear RNA (snRNA) and messenger RNA (mRNA) and is involved in their export from the nucleus.
NCBP2 is also known as CBC2, CBP20, NIP1, PIG55.
