Nuclear trafficking of the POZ-ZF protein Znf131.
Znf131 is a member of the BTB/POZ family of transcription factors with roles in development and carcinogenesis. Like many members of this protein family, Znf131 displays robust nuclear localization in cultured cells, but the mechanism(s) of Znf131 nuclear trafficking is unknown. Here, we report the mechanism of Znf131 nuclear localization. Visual inspection of the Znf131 amino acid sequence revealed three basic regions (BR-1, -2 and -3) with the potential to serve as nuclear localization signals (NLS). Of the three basic regions, only BR-1 functioned independently to efficiently target heterologous beta-gal-GFP fusion proteins to HeLa cell nuclei. However, a Znf131 truncation mutant containing BR-2 and BR-3 efficiently targeted heterologous beta-gal-GFP fusion proteins to HeLa cell nuclei. Mutational analysis of full-length GFP-tagged Znf131 revealed that loss of any one BR alone did not prevent Znf131 nuclear localization. This apparent redundancy in NLS activity was due to the fact that intact BR-1 or BR-2 alone could target full-length Znf131 to nuclei. Consequently, simultaneous mutation of BR-1 and BR-2 abolished full-length Znf131 nuclear localization. Therefore, BR-1 and BR-2 are functional NLSs for Znf131 and as such are designated NLS-1 and NLS-2. Finally, wild type Znf131, and not a Znf131 NLS-defective mutant (NLS-1m/NLS-2m) interacted preferentially with the nuclear import receptor Importin-alpha3 in vitro.
Donaldson
Nickett S
NS
Department of Biology, LSB-331 McMaster University, 1280 Main Street West Hamilton, Canada ON L8S 4K1.
Daniel
Yasmin
Y
Kelly
Kevin F
KF
Graham
Monica
M
Daniel
Juliet M
JM
D000595:Amino Acid Sequence; D000818:Animals; D002452:Cell Count; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D050505:Mutant Proteins; D019913:Nuclear Localization Signals; D011956:Receptors, Cell Surface; D014157:Transcription Factors; C519599:ZNF131 protein, human; C519600:ZNF131 protein, mouse