Involved in the nuclear export of mRNA species bearing retroviral constitutive transport elements (CTE) and in the export of mRNA from the nucleus to the cytoplasm. The NXF1-NXT1 heterodimer is involved in the export of HSP70 mRNA in conjunction with ALYREF/THOC4 and THOC5. Belongs to the NXF family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.