Importin 13 — a round trip through the nuclear pore

In eukaryotic cells DNA and transcription of RNAs are separated from protein biosynthesis occurring in the cytoplasm. Nucleus and cytoplasm are only connected via the nuclear pores. Transport between the compartments is aided by dedicated shuttling proteins, the karyopherins. Most karyopherins carry cargo only in one direction, either into (importins) or out of the nucleus (exportins), and then return empty handed. Importin 13 is an unusual karyopherin that can both import and export cargo. Our work revealed how Imp13 recognizes its cargoes and functions as a bidirectional transport factor.