RNA-seq libraries were prepared with ScriptSeq v2 (Illumina), QuantSeq (Lexogen), or SMARTer Pico v2 (Takara) kits. Splicing isoform quantification was performed using MISO and rMATS packages. The bind-n-Seq experiment was performed as previously described (45 (link)), with minor modifications. Targeted DMS-MaPseq was performed as previously described (33 (link)), with minor modifications. SNRPA1 irCLIP-seq was performed as described (39 (link)), with minor modifications.