Proteomic analysis of the 20S proteasome (PSMA3)-interacting proteins reveals a functional link between the proteasome and mRNA metabolism

► Proteomic analysis revealed over a hundred of PSMA3-interacting proteins. ► A large portion of the PSMA3-interacting proteins belong to mRNA metabolism. ► Proteasomes repress alternative splicing of the SMN1 gene. ► Repression of splicing by proteasomes does not depend on the proteolytic activities.