PTBP1 and breast cancer: PRMT5-mediated symmetric arginine dimethylation of H4R3 (H4R3me2s) at the TCF3 splicing locus is responsible for DNMT3A-MECP2-PTBP1-mediated regulation of TCF3 alternative splicing leading to the production of a pro-invasive TCF3-18B isoform which thereby promotes EMT in breast cancer hypoxia (Fig 7).