Figure 4.

Importin α acts as a negative regulator for the nuclear import of certain proteins. TRF1 and Snail are transported into the nucleus by the importin β1-mediated pathway. In the presence of importin α, TRF1 forms a complex with importin α/β1 heterodimer by binding to importin β1, but this complex remains in the cytoplasm. In contrast, importin α competes with the binding of importin β1 to Snail zinc finger domain, resulting in the inefficient nuclear accumulation of Snail. S-nitrosylation of CRM1 by NO inhibits its binding to NES-containing cargos.