TIF1γ protein regulates epithelial-mesenchymal transition by operating as a small ubiquitin-like modifier (SUMO) E3 ligase for the transcriptional regulator SnoN1

J Biol Chem. 2014 Sep 5;289(36):25067-78. doi: 10.1074/jbc.M114.575878. Epub 2014 Jul 24.


Epithelial-mesenchymal transition (EMT) is a fundamental cellular process that contributes to epithelial tissue morphogenesis during normal development and in tumor invasiveness and metastasis. The transcriptional regulator SnoN robustly influences EMT in response to the cytokine TGFβ, but the mechanisms that regulate the fundamental role of SnoN in TGFβ-induced EMT are not completely understood. Here we employ interaction proteomics to uncover the signaling protein TIF1γ as a specific interactor of SnoN1 but not the closely related isoform SnoN2. A 16-amino acid peptide within a unique region of SnoN1 mediates the interaction of SnoN1 with TIF1γ. Strikingly, although TIF1γ is thought to act as a ubiquitin E3 ligase, we find that TIF1γ operates as a small ubiquitin-like modifier (SUMO) E3 ligase that promotes the sumoylation of SnoN1 at distinct lysine residues. Importantly, TIF1γ-induced sumoylation is required for the ability of SnoN1 to suppress TGFβ-induced EMT, as assayed by the disruption of the morphogenesis of acini in a physiologically relevant three-dimensional model of normal murine mammary gland (NMuMG) epithelial cells. Collectively, our findings define a novel TIF1γ-SnoN1 sumoylation pathway that plays a critical role in EMT and has important implications for our understanding of TGFβ signaling and diverse biological processes in normal development and cancer biology.

Keywords: Cell Signaling; Epithelial-Mesenchymal Transition (EMT); Protein-Protein Interaction; SnoN; Sumoylation; TIF1γ; Transforming Growth Factor β (TGFβ).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites / genetics
  • Blotting, Western
  • Cell Culture Techniques
  • Cell Line
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Epithelial-Mesenchymal Transition / drug effects
  • Epithelial-Mesenchymal Transition / genetics*
  • Gene Expression / drug effects
  • HEK293 Cells
  • Hep G2 Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Mammary Glands, Animal / cytology
  • Mammary Glands, Animal / metabolism
  • Mice
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Protein Binding
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Homology, Amino Acid
  • Sumoylation / drug effects
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transforming Growth Factor beta / pharmacology
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism


  • Intracellular Signaling Peptides and Proteins
  • Proto-Oncogene Proteins
  • SKIL protein, human
  • TRIM33 protein, human
  • Transcription Factors
  • Transforming Growth Factor beta
  • Ubiquitin-Protein Ligases