Human RNF113A participates of pre‐mRNA splicing in vitro

Pre-messenger RNA (mRNA) splicing is an essential step in the control of eukaryotic gene expression. During splicing, the introns are removed from the gene transcripts as the exons are ligated to create mature mRNA sequences. Splicing is performed by the spliceosome, which is a macromolecular complex composed of five small nuclear RNAs (snRNAs) and more than 100 proteins. Except for the core snRNP proteins, most spliceosome proteins are transiently associated and presumably involved with the regulation of spliceosome activity. In this study, we explored the association and participation of the human protein RNF113A in splicing. The addition of excess recombinant RNF113A to in vitro splicing reactions results in splicing inhibition. In whole-cell lysates, RNF113A co-immunoprecipitated with U2, U4, and U6 snRNAs, which are components of the tri-snRNP, and with proteins PRP19 and BRR2. When HeLa cells were CRISPR-edited to reduce the RNF113A levels, the in vitro splicing efficiency was severely affected. Consistently, the splicing activity was partially restored after the addition of the recombinant GST-RNF113A. On the basis on these results, we propose a model in which RNF113A associates with the spliceosome by interacting with PRP19, promoting essential rearrangements that lead to splicing.