Importin 8 (IPO8)

Importin 8 is a member of a class of approximately 20 potential Ran targets that share a sequence motif related to the Ran-binding site of importin-beta. This protein binds to the nuclear pore complex and, along with RanGTP and RANBP1, inhibits the GAP stimulation of the Ran GTPase.

Human RANBP8 and Xenopus RanBP7 share 61% amino acid identity. They both belong to a Ran-binding protein superfamily whose members share with importin-beta an N-terminal sequence motif that appears to account for RanGTP binding. IPO8 was required for AGO2 binding to a large set of target mRNAs, and knockdown of IPO8 led to a moderate increase of target mRNAs. Knockdown of IPO8 had no effect on AGO stability, miRNA biogenesis, or miRNA loading onto AGO proteins.