Updated project metadata. We used in vivo PIR-based crosslinking to assess specific regions of interaction and protein structure of the spliceosomal C complex components hnRNPA1, A2/B1, and C, and the RALY protein. Our results indicate the interaction of proteins of the C complex via domains regions and conserved motifs, posing as evidence of a coordinated action of known regulatory sequences of RBPs. Moreover, the crosslinking information helped to model some of the RBPs, being complementary to other structural methods available.