Protein transport across the nucleus is a selective, multi-step 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 alpha 1 and karyopherin beta1 subunits. Karyopherin alpha 1 functions in the recognition and targeting of substrates destined for nuclear import, while karyopherin beta 1 serves as an adapter, tethering the karyopherin alpha 1/substrate complex to docking proteins on the nuclear envelope, termed nucleoporins. Karyopherin alpha 2 has been shown to complex with Epstein-Barr virus nuclear antigen 1 (EBNA-1). Karyopherin beta 2 and karyopherin beta 2B (also designated transportin 1 and transportin 2) share 84% sequence identity at the amino acid level, however, they have been shown to have different substrate specificities. Karyopherin beta 2 mediates hnRNPA1 nuclear import while karyopherin beta 2B has been implicated in the export of cellular mRNAs through complexes formed with the mRNA export factor TAP.
Function:
Transportin 2 (TNPO2) mediates nuclear import of HuR protein in vitro. It also participates in mRNA export from the nucleus.
Subcellular Location:
Cytoplasm Nucleus
Similarity:
Belongs to the importin beta family.
Contains 13 HEAT repeats.
Contains 1 importin N-terminal domain.
SWISS:
O14787
Gene ID:
30000
Database links:
Entrez Gene: 30000 Human
Entrez Gene: 212999 Mouse
Entrez Gene: 304670 Rat
Omim: 603002 Human
SwissProt: O14787 Human
SwissProt: Q6IN77 Human
SwissProt: Q99LG2 Mouse
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