Nuclear localization signal

A nuclear localizing signal (NLS) is a peptide "tag" on the exposed surface of a protein that interacts with nuclear membrane proteins to confine the polypeptide to a cell's nucleus. Different nuclear localized proteins may share the same NLS.

Genetically the NLS results from transcription of a nuclear localizing sequence. Cellular processes and protein function may be studied by adding a known NLS sequence to a gene, confining the chimeric protein product to the nucleus. A NLS is the opposite of a nuclear export signal, which confines proteins to the cytosolic face of the nuclear membrane.