RNA-binding protein which binds to intronic polypyrimidine tracts and mediates negative regulation of exons splicing. May antagonize in a tissue-specific manner the ability of NOVA1 to activate exon selection. In addition to its function in pre-mRNA splicing, plays also a role in the regulation of translation. Reduced affinity for RNA. Monomer. Interacts with NOVA1; the interaction is direct. Identified in a mRNP complex, at least composed of DHX9, DDX3X, ELAVL1, HNRNPU, IGF2BP1, ILF3, PABPC1, PCBP2, PTBP2, STAU1, STAU2, SYNCRIP and YBX1. Part of a ternary complex containing KHSRP and HNRPH1 (PubMed:11003644, PubMed:19029303). Interacts with NOVA2; the interaction is direct (By similarity). Mainly expressed in brain although also detected in other tissues like heart and skeletal muscle. Isoform 1 and isoform 2 are specifically expressed in neuronal tissues. Isoform 3 and isoform 4 are expressed in non-neuronal tissues. Isoform 5 and isoform 6 are truncated forms expressed in non-neuronal tissues.