Identification of a nuclear localization signal in mouse polycomb protein, M33

Zoolog Sci. 2006 Sep;23(9):785-91. doi: 10.2108/zsj.23.785.


The mouse Polycomb group (PcG) protein M33 forms nuclear complexes with the products of other PcG members and maintains repressed states of developmentally important genes, including homeotic genes. In this context, nuclear localization is a prerequisite for M33 to exert its function. However, we previously found that M33 in mouse liver shuttles dynamically between the nucleus and the cytoplasm, depending on the proliferative states of cells, coupled with phosphorylation and dephosphorylation of M33 protein. To understand the mechanism and significance of this phenomenon, we identified the functional nuclear localization signal (NLS) of M33 protein. Deletion mutants that lack a particular one of three putative NLS motifs failed to localize in the nucleus. Green fluorescent protein (GFP) fused to this motif specifically localized in the nucleus. We conclude that this amino-acid stretch in M33 acts as the functional NLS for this protein.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA Mutational Analysis / methods
  • Gene Order / genetics
  • Green Fluorescent Proteins / analysis
  • Mice / genetics*
  • Mice / physiology
  • Microscopy, Fluorescence / methods
  • Mutant Proteins / analysis
  • Mutant Proteins / biosynthesis
  • NIH 3T3 Cells
  • Nuclear Localization Signals / genetics*
  • Nuclear Localization Signals / physiology
  • Plasmids
  • Polycomb Repressive Complex 1
  • Polycomb-Group Proteins
  • Repressor Proteins / genetics*
  • Repressor Proteins / physiology


  • Cbx2 protein, mouse
  • Mutant Proteins
  • Nuclear Localization Signals
  • Polycomb-Group Proteins
  • Repressor Proteins
  • Green Fluorescent Proteins
  • Polycomb Repressive Complex 1