RNA-binding protein that plays a role in the regulation of alternative splicing and influences mRNA splice site selection and exon inclusion. Binds both poly(A and poly(U homopolymers. Phosphorylation by PTK6 inhibits its RNA-binding ability (By similarity. Induces an increased concentration-dependent incorporation of exon in CD44 pre-mRNA by direct binding to purine-rich exonic enhancer. Can regulate alternative splicing of NRXN1 in the laminin G-like domain 6 containing the evolutionary conserved neurexin alternative spliced segment 4 (AS4 involved in neurexin selective targeting to postsynaptic partners. Regulates cell-type specific alternative splicing of NRXN1 at AS4 and acts synergystically with SAM68 in exon skipping. In contrast acts antagonistically with SAM68 in NRXN3 exon skipping at AS4. Its phosphorylation by FYN inhibits its ability to regulate splice site selection. May function as an adapter protein for Src kinases during mitosis.