Transcriptome-wide analysis of U2AF2 RNA binding in a human hematopoietic cell line.

The essential pre-mRNA splicing factor U2AF2 (also called U2AF65) identifies polypyrimidine (Py) tract signals of nascent transcripts, despite length and sequence variations. Previous studies have shown that the U2AF2 RNA recognition motifs (RRM1 and RRM2) preferentially bind uridine-rich RNAs. Nonetheless, the specificity of the RRM1/RRM2 interface for the central Py tract nucleotide has yet to be investigated. Enhanced crosslinking and immunoprecipitation of endogenous U2AF2 in human erythroleukemia cells showed uridine-sensitive binding sites with lower sequence conservation at the central nucleotide positions of otherwise uridine-rich, U2AF2-bound splice sites. Altogether, these results highlight the importance of RNA flexibility for protein recognition and take a step towards relating splice site motifs to pre-mRNA splicing efficiencies. Keywords: splicing, RNA binding, U2AF2, U2AF65, 3'SS, 3' splice site, eCLIP, polypyrimidine tract, RNA recognition motif, RRM, U-rich, Py-tract Overall design: In this study, we performed high-throughput sequencing of RNA isolated by enhanced crosslinking immunoprecipitation (eCLIP-seq) to determine U2AF2-RNA binding in the context of a human hematopoietic cell line (HEL). Experiments were performed in biological duplicate.