Stimulator of protein export for NES-containing proteins (PubMed:10567585). Also plays a role in the nuclear export of U1 snRNA, tRNA, and mRNA (PubMed:10848583). The NXF1-NXT1 heterodimer is involved in the export of HSP70 mRNA in conjunction with ALYREF/THOC4 and THOC5 (PubMed:11259602, PubMed:19165146).