Required for mRNA export from the nucleus to the cytoplasm. Acts as an adapter that uses the DDX39B/UAP56-NFX1 pathway to ensure efficient mRNA export and delivering to the nuclear pore. Associates with spliced and unspliced mRNAs simultaneously with ALYREF/THOC4 (By similarity). Interacts with DDX39B/UAP56 and NXF1; interaction with DDX39B/UAP56 and NXF1 are mutually exclusive. Interacts with SSRP1; required for its recruitment to mRNAs. Interacts with CHTOP (By similarity). Belongs to the UIF family.