The nuclear localization signal of zebrafish terra is located within the DM domain

Zebrafish Terra is a member of the DM domain-containing transcription factor family and is involved in somitogenesis. The other known members of this family play a role in sex differentiation across species from Caenorhabditis elegans to human. Using the green fluorescence protein-Terra fusion constructs, we have identified the nuclear localization signal (NLS) of terra by transfecting human HeLa cells. The terra NLS is located between the two intertwined zinc-binding sites of the DNA-binding domain. However, the nuclear translocation of terra is independent of the structure required for DNA binding. Mutational analysis demonstrates that basic residues K77 and R78 within the DM domain are absolutely required for the translocation of Terra into the nuclei. Sequence comparison discloses that the NLS of Terra is also present in the other known members of the DM family, indicating the conservative nature of the NLS of this family during evolution.