Figure 3. Cytoplasmic chaperones shuttle into the nucleus under various conditions.

(A) Several cytoplasmic chaperones contain nuclear-targeting peptide signals and can be imported into the nucleus by RanGTP-mediated mechanisms in ambient growth conditions. (B) Cytoplasmic chaperones shuttle into the nucleus upon acute environmental stress. For Hsp70, this transport occurs independently of RanGTP and is mediated by the Hikeshi protein. (C) Chaperones are found associated with nuclear aggregates composed of disease-associated proteins, i.e. chronic nuclear misfolding stress. It is thus far unclear how these chaperones are transported into the nucleus under these conditions.