Background information
Protein transport across the nucleus is a selective, multi-step process involving several cytoplasmic factors that mediate protein passage through the nuclear pore complex (NPC). Cytoplasmic proteins that contain nuclear localization signals (NLSs) must be recognized as import substrates, dock at the nuclear pore complex and translocate across the nuclear envelope in an ATP-dependent fashion. Karyopherin alpha 1 and karyopherin alpha 6 are widely expressed nuclear import proteins that act as adaptors for karyopherin ∫1, specifically binding to and guiding NLS-containing proteins to the NPC. Both karyopherin alpha 1 and karyopherin alpha 6 contain one IBB domain and ten ARM repeats through which they convey their protein binding and localization function. Together, karyopherin å1 and karyopherin å6 are responsible for ensuring the nuclear import of NLS-containing substrates
