The vertebrate Tap protein is a member of the NXF family of shuttling transport receptors for nuclear export of mRNA. Tap has a modular structure, and its most C-terminal domain is important for binding to FG repeat-containing nuclear pore proteins (FG-nucleoporins) and is sufficient to mediate nuclear shuttling [ PUBMED:11875519 … expand

The vertebrate Tap protein is a member of the NXF family of shuttling transport receptors for nuclear export of mRNA. Tap has a modular structure, and its most C-terminal domain is important for binding to FG repeat-containing nuclear pore proteins (FG-nucleoporins) and is sufficient to mediate nuclear shuttling [ PUBMED:11875519 ]. The structure of the C-terminal domain is composed of four helices [ PUBMED:11875519 ]. The structure is related to the UBA domain.

The NXF family of mRNA nuclear export factors includes vertebrate NXF1 (also called tip-associated protein or mRNA export factor TAP), NXF2 (also called cancer/testis antigen CT39 or TAP-like protein TAPL-2), Caenorhabditis elegans NXF1 (ceNXF1), Saccharomyces cerevisiae mRNA nuclear export factor Mex67p and similar proteins. NXF proteins can stimulate nuclear export of mRNAs and facilitate the export of unspliced viral mRNA containing the constitutive transport element. An NXF protein is multi-domain with a nuclear localization sequence (NLS), a non-canonical mRNA-binding domain, and four leucine-rich repeats (LLR) at the N-terminal region. Its C-terminal part contains a NTF2-like domain and a ubiquitin-associated (UBA)-like domain, joined by flexible Pro-rich linker. Caenorhabditis elegans NXF1 are essential for the nuclear export of poly(A)+mRNA. In budding yeast, Mex67p binds mRNAs through its adaptor Yra1/REF. It also interacts directly with Nab2, an essential shuttling mRNA-binding protein required for export. Moreover, Mex67p associates with both nuclear pore protein (nucleoporin) FG repeats and Hpr1, a component of the TREX/THO complex linking transcription and export [ PUBMED:11875519 PUBMED:20810649 PUBMED:10567585 PUBMED:11073998 PUBMED:11583626 PUBMED:12581645 PUBMED:19401465 PUBMED:11060011 PUBMED:11256625 PUBMED:10668806 PUBMED:11259411 PUBMED:9660949 PUBMED:9175835 PUBMED:10454577 PUBMED:10323864 PUBMED:10202158 ].