Required for pre-mRNA splicing and for exon-junction complex (EJC) assembly. Hinders eIF4AIII from non-specifically binding RNA and escorts it to the splicing machinery to promote EJC assembly on mature mRNAs. Component of the spliceosome C complex (By similarity). Interacts with eIF4AIII (PubMed:22961380). Belongs to the CWC22 family. Truncated N-terminus.