mouse monoclonal IgG1; Protein transport across the nucleus is a selective, multistep process involving several cytoplasmic factors. Proteins must be recognized as import substrates, dock at the nuclear pore complex and translocate across the nuclear envelope in an ATP-dependent fashion. Two cytosolic factors centrally involved in the recognition and docking process are the karyopherin-α and karyopherin-β proteins. The karyopherin holoenzyme is a heterodimer of α and β subunits. Karyopherin-α functions in the recognition and targeting of substrates destined for nuclear import, while karyopherin-β serves as an adapter, tethering the karyopherin-a/substrate complex to docking proteins on the nuclear envelope termed nucleoporins. p62 glycoprotein is one such nucleoporin, and is not only involved in the nuclear import of proteins, but also the export of nascent mRNA strands. An additional protein, NTF2 (nuclear transport factor 2), interacts with nucleoporin p62 as a homodimer, and may be an obligate component of functional p62.