PTBP1 and cancer: To uncover which regulators can best explain splicing in glioblastomas, we next applied MAPP to cancer samples29, where it inferred that the PTBP-binding motif has the most significant activity on pre-mRNA processing (Supplementary Data 4, 5) with a motif ranking and position-dependent activity that matches the profile obtained from the PTBP1/2 knock-down data (Fig. 4a, b and Supplementary Data 6).