The sequence [EKRKI(E/R)(K/L/R/S/T)] is a nuclear localization signal for importin 7 binding (NLS7).

BACKGROUND: Nuclear translocation of large proteins is mediated through specific protein carriers, collectively named karyopherins (importins, exportins and adaptor proteins). Cargo proteins are recognized by importins through specific motifs, known as nuclear localization signals (NLS). However, only the NLS recognized by importin α and transportin (M9 NLS) have been identified so far METHODS: An unsupervised in silico approach was used, followed by experimental validation.

RESULTS: We identified the sequence EKRKI(E/R)(K/L/R/S/T) as an NLS signal for importin 7 recognition. This sequence was validated in the breast cancer cell line T47D, which expresses importin 7. Finally, we verified that importin 7-mediated nuclear protein transport is affected by cargo protein phosphorylation.

CONCLUSIONS: The NLS sequence for importin 7 was identified and we propose this approach as an identification method of novel specific NLS sequences for β-karyopherin family members.

GENERAL SIGNIFICANCE: Elucidating the complex relationships of the nuclear transporters and their cargo proteins may help in laying the foundation for the development of novel therapeutics, targeting specific importins, with an immediate translational impact.