Component of the CBC complex, which binds co-transcriptionally to the cap of pre-mRNAs and is involved in maturation, export and degradation of nuclear mRNAs. The CBC complex is required for efficient pre-mRNA splicing through efficient commitment complex and spliceosome formation. Together with NPL3, the CBC complex is required for export of mRNAs out of the nucleus. The CBC complex is also involved in nuclear mRNA degradation, probably by directing the mRNAs to the sites of degradation. Affects replication of the positive-strand RNA virus BMV. Component of the nuclear cap-binding complex (CBC), a heterodimer composed of STO1/CBC1 and CBC2 that interacts with capped RNAs. The complex interacts strongly with the importin subunit alpha SRP1. The SRP1-CBC trimer also binds to capped RNAs, but formation of the importin alpha/beta heterodimer upon binding of KAP95 to SRP1 in the cytoplasm causes dissociation of CBC from the RNA. The CBC complex is part of the commitment complex 1 (CC1), binding to the cap of pre-mRNA and interacting with U1 snRNP subunits MUD2 and SNU56. The CBC complex is part of the NRD1 complex, composed of CBC2, NAB1, NRD1, SEN1 and STO1/CBC2. The CBC complex also interacts with NPL3 and eIF4G (TIF4631 and TIF4632). Predominantly nuclear, is able to exit the nucleus in an RNA-dependent manner. In contrast to metazoans, where the CBC complex is involved in the nuclear export of capped U snRNAs, it is believed that in yeast, U snRNAs are not exported from the nucleus and U snRNPs are assembled in the nucleus from RNAs and imported proteins. Present with 6200 molecules/cell in log phase SD medium. Belongs to the RRM NCBP2 family.