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.[2][3] 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.[4] 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.[5][6]
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).
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 poreproteins (FG-nucleoporins) and is sufficient to mediate nuclear shuttling.[14][15]
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.[14][15]
Function
Nuclear export of mRNAs is mediated by the Tap protein.
Structure
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.
References
↑Yoon DW, Lee H, Seol W, DeMaria M, Rosenzweig M, Jung JU (May 1997). "Tap: a novel cellular protein that interacts with tip of herpesvirus saimiri and induces lymphocyte aggregation". Immunity. 6 (5): 571–82. doi:10.1016/S1074-7613(00)80345-3. PMID9175835.
↑ 2.02.1Grüter P, Tabernero C, von Kobbe C, et al. (April 1998). "TAP, the human homolog of Mex67p, mediates CTE-dependent RNA export from the nucleus". Mol. Cell. 1 (5): 649–59. doi:10.1016/S1097-2765(00)80065-9. PMID9660949.
↑Zolotukhin, Andrei S; Tan Wei; Bear Jenifer; Smulevitch Sergey; Felber Barbara K (February 2002). "U2AF participates in the binding of TAP (NXF1) to mRNA". J. Biol. Chem. United States. 277 (6): 3935–42. doi:10.1074/jbc.M107598200. ISSN0021-9258. PMID11724776.
↑Tang, H; Wong-Staal F (October 2000). "Specific interaction between RNA helicase A and Tap, two cellular proteins that bind to the constitutive transport element of type D retrovirus". J. Biol. Chem. UNITED STATES. 275 (42): 32694–700. doi:10.1074/jbc.M003933200. ISSN0021-9258. PMID10924507.
↑Saito, Kuniaki; Fujiwara Toshinobu; Katahira Jun; Inoue Kunio; Sakamoto Hiroshi (August 2004). "TAP/NXF1, the primary mRNA export receptor, specifically interacts with a neuronal RNA-binding protein HuD". Biochem. Biophys. Res. Commun. United States. 321 (2): 291–7. doi:10.1016/j.bbrc.2004.06.140. ISSN0006-291X. PMID15358174.
↑Schmitt, I; Gerace L (November 2001). "In vitro analysis of nuclear transport mediated by the C-terminal shuttle domain of Tap". J. Biol. Chem. United States. 276 (45): 42355–63. doi:10.1074/jbc.M103916200. ISSN0021-9258. PMID11551912.
↑ 14.014.1Grant RP, Hurt E, Neuhaus D, Stewart M (April 2002). "Structure of the C-terminal FG-nucleoporin binding domain of Tap/NXF1". Nat. Struct. Biol. 9 (4): 247–51. doi:10.1038/nsb773. PMID11875519.