Component of the cap-binding complex (CBC), which binds co-transcriptionally to the 5' cap of pre-mRNAs and is involved in various processes such as pre-mRNA splicing and RNA-mediated gene silencing (RNAi). The CBC complex is involved in miRNA-mediated RNA interference and is required for primary microRNAs (miRNAs) processing. In the CBC complex, ncbp2 recognizes and binds capped RNAs (m7GpppG-capped RNA) but requires ncbp1 to stabilize the movement of its N-terminal loop and lock the CBC into a high affinity cap-binding state with the cap structure (By similarity). Component of the nuclear cap-binding complex (CBC), a heterodimer composed of ncbp1 and ncbp2 that interacts with m7GpppG-capped RNA. Belongs to the RRM NCBP2 family.