Nuclear cap-binding complex (CBC)

The nuclear cap-binding complex (CBC), also known as CBC80/20, is a heterodimeric protein complex present in all eukaryotes, composed of two subunits: CBP20 (also known as NCBP2) and CBP80 (also known as NCBP1)[1][2][3][6]. The complex binds tightly and cotranscriptionally to the 5'-cap structure (m^7^GpppN) of nascent RNA polymerase II transcripts[5][7]. NCBP2/CBP20 contains the primary cap-binding pocket, while NCBP1/CBP80 stabilizes this interaction and is essential for high-affinity cap binding[1][2][3][5]. CBC protects mRNA from 5'–3' degradation, contributes to pre-mRNA splicing, nuclear export, and the first round of mRNA translation in the cytoplasm before being replaced by eIF4E for steady-state translation[1][4][5]. Both subunits can bind RNA directly. The CBC forms a platform for interaction with other nuclear factors such as PHAX, ARS2, and NELF-E, which influence the fate of transcripts, including histone mRNA processing, snRNA export, and other gene-specific effects[5][3]. Altered CBC function is implicated in cancer and neurological diseases, but it is generally not considered a direct therapeutic target[4][3][6]. Current evidence does not support CBC as a common drug target, and there are no known small-molecule drugs or specific therapies directly aimed at CBC components in clinical use or trial[6]. CBC’s central role in fundamental RNA metabolism makes it a potentially risky target due to possible toxicity, but its involvement in disease processes such as cancer is an area of ongoing research[4][3]. CBC is an essential heterodimeric nuclear complex central to mRNA processing, not recognized as a therapeutic drug target, but highly relevant to gene expression regulation and certain disease mechanisms[1][2][6][3][4][5].

Other names

Cap-binding complexCap-binding protein complexCBC80/20Nuclear cap-binding protein complexCBP80/20NCBP (Nuclear cap-binding protein)CBP20-CBP80 complex