Based on limited published evidence, SON is an RNA-binding protein that functions as a splicing cofactor promoting efficient mRNA splicing of transcripts with weak splice sites. SON facilitates interactions between SR-proteins and RNA polymerase II, and regulates splicing of cell-cycle, DNA-repair, and brain-development genes including TUBG1, AURKB, and FLNA 1. The protein also binds DNA and may repress hepatitis B virus transcription. SON is essential for neuronal migration and metabolism, with mutations causing ZTTK syndrome. GO annotations highlight roles in microtubule organization, mitotic cytokinesis, and apoptotic regulation.