Probing Novel SAP18 Interactions within Spliceosomal Complex by Proximity-dependent BioID Approach

Abstract

Biochemical and proteomic studies have revealed that pre-mRNA splicing is a highly dynamic process mediated primarily by the spliceosome. The spliceosome is composed of small nuclear ribonucleoproteins (snRNPs) together with approximately a hundred RNA-binding proteins (RBPs), and assembles stepwise through distinct complexes (A, B, Bact, C, C*, and P). The exon junction complex (EJC), a multimeric RBP complex, is deposited at exon-exon junctions during the late stages of spliceosome assembly. SAP18, a core component of the EJC-associated ASAP/PSAP complexes, plays a critical role in splicing regulation. However, the precise stage at which SAP18 is assembled into the spliceosome has remained unclear.