DNA demethylation is associated with gene activation and is mediated by a family of ten-eleven translocation (TET) dioxygenase. The TET3 protein is a 1668-amino-acid DNA demethylase that is predicted to possess five nuclear localization signals (NLSs). In this paper, we used a series of green fluorescent protein-tagged and mutation constructs to identify a conserved NLS (KKRK) embedded between amino acid 1615 and 1618 of mouse TET3. The KKRK sequence facilitates the cytoplasmic protein's translocation into the nucleus. Additionally TET3 may be imported into the nucleus by importin-alpha and importin-beta. (C) 2013 Elsevier Inc. All rights reserved.