Splicing factor that specifically promotes exon-inclusion during alternative splicing. Interaction with YTHDC1, a RNA-binding protein that recognizes and binds N6-methyladenosine (m6A)-containing RNAs, promotes recruitment of SRSF3 to its mRNA-binding elements adjacent to m6A sites, leading to exon-inclusion during alternative splicing. Also functions as export adapter involved in mRNA nuclear export. Binds mRNA which is thought to be transferred to the NXF1-NXT1 heterodimer for export (TAP/NXF1 pathway); enhances NXF1-NXT1 RNA-binding activity. Involved in nuclear export of m6A-containing mRNAs via interaction with YTHDC1: interaction with YTHDC1 facilitates m6A-containing mRNA-binding to both SRSF3 and NXF1, promoting mRNA nuclear export. RNA-binding is semi-sequence specific. Interacts with CPSF6 (By similarity). Interacts with RBMY1A1 (By similarity). Interacts with SREK1/SFRS12 (By similarity). Interacts with NXF1 (By similarity). Interacts with YTHDC1, leading to recruitment to RNA elements adjacent to m6A sites (PubMed:29799838). Recruited to nuclear speckles following interaction with YTHDC1. Highest expression in thymus and pre-B cell lines; high, in testis, brain and spleen; very low in heart and not detectable in liver and kidney. Isoform long is induced by serum; in a tissue culture. Phosphorylated by CLK1, CLK2, CLK3 and CLK4. Extensively phosphorylated on serine residues in the RS domain. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the splicing factor SR family.