NXF1

This gene is one member of a family of nuclear RNA export factor genes. Common domain features of this family are a noncanonical RNP-type RNA-binding domain (RBD), 4 leucine-rich repeats (LRRs), a nuclear transport factor 2 (NTF2)-like domain that allows heterodimerization with NTF2-related export protein-1 (NXT1), and a ubiquitin-associated domain that mediates interactions with nucleoporins. Alternative splicing results in transcript variants. The LRRs and NTF2-like domains are required for export activity. The encoded protein of this gene shuttles between the nucleus and the cytoplasm and binds in vivo to poly(A)+ RNA. It is the vertebrate homologue of the yeast protein Mex67p.^[6][7] The encoded protein overcomes the mRNA export block caused by the presence of saturating amounts of CTE (constitutive transport element) RNA of type D retroviruses.^[8] A variant allele of the homologous Nxf1 gene in mice suppresses a class of mutations caused by integration of an endogenous retrovirus (intracisternal A particle) into an intron.^[9][10]

NXF1 has been shown to interact with TNPO2,^[11] MAGOH,^[12] U2 small nuclear RNA auxiliary factor 1,^[13] DHX9,^[14] HuD^[15] and NUP214.^[16][17]

In molecular biology, another name for the protein NXF1 is TAP. In particular this entry focuses on the C-terminal domain, which also contains the UBA (protein domain).

Quick facts TAP_C, Identifiers ...

TAP_C
complex between tap uba domain and fxfg nucleoporin peptide
Identifiers
Symbol	TAP_C
Pfam	PF03943
Pfam clan	CL0214
InterPro	IPR005637
SCOP2	1go5 / SCOPe / SUPFAM
Available protein structures: PDB   IPR005637 PF03943 (ECOD; PDBsum)   AlphaFold IPR005637 PF03943

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This entry contains the NXF family of shuttling transport receptors for nuclear export of mRNA, which include:

• vertebrate mRNA export factor TAP or nuclear RNA export factor 1 (NXF1).
• Caenorhabditis elegans nuclear RNA export factor 1 (nxf-1).
• yeast mRNA export factor MEX67. Members of the NXF family have a modular structure. A nuclear localization sequence and a noncanonical RNA recognition motif (RRM) (see PROSITEDOC) followed by four LRR repeats are located in its N-terminal half. The C-terminal half contains a NTF2 domain (see [href="http://expasy.org/prosite/PDOC50177 PROSITEDOC]) followed by a second domain, TAP-C. The TAP-C domain is important for binding to FG repeat-containing nuclear pore proteins (FG-nucleoporins) and is sufficient to mediate nuclear shuttling.^[18][19]

The Tap-C domain is made of four alpha helices packed against each other. The arrangement of helices 1, 2 and 3 is similar to that seen in a UBA fold. and is joined to the next module by flexible 12-residue Pro-rich linker.^[18][19]

Nuclear export of mRNAs is mediated by the Tap protein.

Tap can form a multimeric complex with itself and with other members of the NXF family. Three functional domains of Tap have been well characterized: the RNA-binding domain, the Nuclear Transport Factor 2 (NTF2)-like domain, and the ubiquitin-associated (UBA) domain.