Nuclear localization signals of the E-cadherin transcriptional repressor Snail.
The E-cadherin transcriptional repressor, Snail, plays a critical role in driving the epithelial-mesenchymal transition programs that mark gastrulation as well as invasion of cancer cells. Recent data suggest that Snail is phosphorylated by GSK3-beta, resulting in beta-TRCP-mediated ubiquitination and proteasomal degradation. Accordingly, Wnt signaling inhibits Snail phosphorylation, and consequently increases Snail protein levels. In the present study, we examine the function of nuclear localization motifs embedded within the Snail sequence. A typical bipartite nuclear localization signal (NLS) motif is located at the N-terminal of Snail, where it overlaps with the SNAG domain (residues 8-16), while a basic cluster NLS motif is found proximal to zinc finger domains (residues 151-152). Mutational inactivation of these NLS signals resulted in decreased levels of nuclear and total Snail protein as well as attenuated Snail repressor activity on an E-cadherin promoter construct, suggesting that NLS motifs are essential for proper function. In the presence of GSK3 inhibitor LiCl, the cytoplasmic levels of the NLS mutants increased, suggesting that cytosolic Snail undergoes rapid phosphorylation and degradation. Given the highly conserved nature of the Snail NLS motifs (from Xenopus to human), these results indicate that nuclear localization signals regulate Snail expression and subcellular localization via GSK3-beta-dependent phosphorylation.
Ko
Hyeonseok
H
Department of Biochemistry and Molecular Biology, Brain Korea 21 Project for Medical Science of Yonsei University, College of Medicine, Seoul, Korea.
Kim
Hyun Sil
HS
Kim
Nam Hee
NH
Lee
Sang Hwy
SH
Kim
Kun Hong
KH
Hong
Su Hyung
SH
Yook
Jong In
JI
D021581:Active Transport, Cell Nucleus; D000409:Alanine / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000235:genetics* / Q000502:physiology; D045744:Cell Line, Tumor; D017124:Conserved Sequence; D004847:Epithelial Cells / Q000166:cytology; D004848:Epithelium / Q000473:pathology; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008648:Mesoderm / Q000166:cytology / Q000473:pathology; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology*
D015820:Cadherins; D019913:Nuclear Localization Signals; D012097:Repressor Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D000409:Alanine