Spliceosomes are multi-protein complexes that are composed of snRNPs (small nuclear ribonucleoproteins) and a variety of associated protein factors, all of which work in concert to regulate the splicing of pre-mRNA, a critical step in the post-transcriptional regulation of gene expression. CWC22 (CWC22 spliceosome-associated protein), also known as NCM, fSAPb or EIF4GL, is a 908 amino acid nuclear protein and component of the spliceosome C complex. CWC22 is associated with the spliceosome prior to catalytic steps and remains associated throughout the reaction. Belonging to the CWC22 family, CW22 contains one MI domain and a MIF4G domain. The gene encoding CWC22 maps to human chromosome 2q31.3. As the second largest human chromosome, chromosome 2 makes up approximately 8% of the human genome and contains 237 million bases encoding over 1,400 genes.