CWC22 is a critical spliceosome-associated protein that performs dual functions in pre-mRNA splicing and exon junction complex (EJC) assembly. As an integral component of the spliceosome, CWC22 is required for efficient pre-mRNA splicing and directly interacts with the core EJC component eIF4AIII 1. The protein prevents eIF4AIII from non-specifically binding RNA and escorts it to the splicing machinery, where it facilitates EJC assembly on mature mRNAs 12. CWC22 depletion causes global splicing defects and downregulation of diverse gene expression pathways 2. Through its role in EJC assembly, CWC22 is essential for nonsense-mediated mRNA decay (NMD) pathway function 3. Structural studies reveal that CWC22 forms a heterodimer with CWC27 and creates an intermediate platform for eIF4AIII recruitment to the spliceosome 45. Clinically, CWC22 dysfunction has been implicated in retinal degeneration and inflammatory processes, with disrupted CWC22 nuclear localization observed in atherosclerotic macrophages leading to impaired splicing regulation 64. The protein's expression levels may serve as prognostic markers in colon cancer 7.