An Interpretable Model of pre-mRNA Splicing for Animal and Plant Genes

Pre-mRNA splicing is a fundamental step in gene expression, conserved across eukaryotes, in which the spliceosome recognizes motifs at the 3 and 5 splice sites (SS), excises introns and ligates exons. SS recognition and pairing is often influenced by splicing regulatory factors (SRFs) that bind to splicing regulatory elements (SREs). Several families of sequence-specific SRFs are known to be similarly ancient. Here, we describe SMsplice, a fully interpretable model of pre-mRNA splicing that combines new models of core SS motifs, SREs, and exonic and intronic length preferences. We learn models the predict SS locations with 83-86% accuracy in fish, insects and plants, and about 70% in mammals. Learned SRE motifs include both known SRF binding motifs as well as novel motifs, and both classes are supported by genetic analyses. Our comparisons across species highlight similarities between non-mammals and a greater reliance on SREs in mammalian splicing, and increased reliance on intronic SREs in plant splicing.