Nuclear RNA export factor 3 (NXF3) is a member of the nuclear RNA export factor (NXF) family of proteins, which plays a role in mediating the export of cellular mRNA from the nucleus to the cytoplasm for translation. Like NXF1 and NFX2, NXF3 has the ability to bind and export mRNA from the nucleus to the cytoplasm, but it uses a completely different mechanism []. The expression of NXF3 appears to be restricted to the testis [].
Mex67 is involved in the export of mRNA from the nucleus to the cytoplasm in Saccharomyces cerevisiae []. Vertebrate TAP (also called NXF1 for nuclear RNA export factor 1) is the orthologue of Mex67 []. TAP belongs to a multigene family with conserved modular architecture []. Other members of the family in humans are NXF2, NXF3, and NFX5. Both TAP(NXF1) and NXF2 bind mRNA and display RNA nuclear export activity []. NXF3 also has the ability to export mRNA from the nucleus to the cytoplasm but it uses a different mechanism []. NXF1 and NXF2 are predominantly nuclear, whereas the cytoplasmic presence of NXF3 and NXF5 suggests that they have a different cellular function [, ].Three functional domains of TAP have been characterised: the RNA-binding domain, the Nuclear Transport Factor 2 (NTF2)-like domain, and the ubiquitin-associated (UBA) domain. The RNA-binding domain (RBD) of TAP is located at its amino terminus and is composed of two RNA recognition motifs (RRMs) and one leucine-rich region [, ]. Once bound to mRNA, TAP escorts the messenger ribonucleoprotein (mRNP) to the nuclear pore, where TAP interacts with nucleoporins via the NTF2-like (NTF2L) and UBA domains [].
