Categories and Research Strategies of Nuclear Localization Signal

The nuclear pore complex(NPC) is in charge of the exchange of macromolecules between the nuclei and the cytoplasm of eucaryotic cells.The small compounds can get into the nuclei through the NPC freely or by passive diffusion.However,those proteins whose molecular weights are larger than 50 kD can only get into nuclei by active transport.There must be one or more special signals in the amino acid sequences,so-called nuclear localization signals,which can be recognized by respective karyopherins,in those proteins.There are diverse sequences in NLSs,including classical NLS(cNLS),PY-NLS,which can be recognized by importin β2,and some other NLSs.Though there are similar properties among the same family members of NLSs,there is no fully conserved amino acid sequence.Different NLSs often correspond to different mechanisms of nuclear transport,and also,couple of functional NLSs may exist in one certain protein.The studies on NLS help us not only reveal new nuclear transport mechanism of macromolecules,but also discover new functions of proteins.Categories of NLSs were summarized by the authors.Two common-used software employed in NLS prediction and the strategies used to identify NLS are also introduced in this review.