Polypyrimidine tract-binding protein 1 is a protein that in humans is encoded by the PTBP1 gene. It plays a role in pre-mRNA splicing and in the regulation of alternative splicing events. PTBP1 activates exon skipping of its own pre-mRNA during muscle cell differentiation. It binds to the polypyrimidine tract of introns and may promote RNA looping when bound to two separate polypyrimidine tracts in the same pre-mRNA. PTBP1 may promote the binding of U2 snRNP to pre-mRNA. It cooperates with RAVER1 to modulate switching between mutually exclusive exons during maturation of the TPM1 pre-mRNA. Represses the splicing of MAPT/Tau exon 10.