NXF1TAP

NXF1TAP, commonly referred to as TAP (nuclear export factor 1), is a central component of the eukaryotic mRNA export machinery. In vertebrates it acts as the principal receptor that mediates the export of mRNA from the nucleus to the cytoplasm. NXF1 forms a heterodimer with the small partner NXT1 (p15), and together they ferry mRNA through the nuclear pore complex.

Mechanism: The NXF1–NXT1 complex associates with mRNA via export cofactors and adapters such as Aly/REF and components of the THO/TREX complex. This assembly enables binding to FG-repeat nucleoporins in the nuclear pore, allowing selective translocation of mature mRNPs into the cytoplasm. The export process is coordinated with RNA processing and translation readiness, and the receptor itself does not harbor intrinsic ATPase activity; energy and directionality are provided by interactions with the pore and associated cofactors.

Structure and evolution: NXF1 is a modular protein with regions that mediate RNA binding, protein interactions, and docking to the nuclear pore complex. It is evolutionarily conserved across eukaryotes; the budding yeast Mex67p is a functional homolog that forms a similar complex with Mtr2p (the yeast equivalent of NXT1). The vertebrate NXF1–NXT1 heterodimer represents a widely conserved export pathway for most cellular mRNA transcripts.

Clinical and research relevance: NXF1/TAP is essential for cellular viability; depletion or dysfunction leads to nuclear accumulation of polyadenylated RNA and growth defects. It is a focal point in studies of gene expression regulation, RNA processing, and diseases where mRNA export is perturbed. Research areas include the regulation of mRNA export during development and in response to cellular stress.