title: Nuclear ubiquitination by FBXL5 modulates Snail1 DNA binding and stability.
abstract: The zinc finger transcription factor Snail1 regulates epithelial to mesenchymal transition, repressing epithelial markers and activating mesenchymal genes. Snail1 is an extremely labile protein degraded by the cytoplasmic ubiquitin-ligases β-TrCP1/FBXW1 and Ppa/FBXL14. Using a short hairpin RNA screening, we have identified FBXL5 as a novel Snail1 ubiquitin ligase. FBXL5 is located in the nucleus where it interacts with Snail1 promoting its polyubiquitination and affecting Snail1 protein stability and function by impairing DNA binding. Snail1 downregulation by FBXL5 is prevented by Lats2, a protein kinase that phosphorylates Snail1 precluding its nuclear export but not its polyubiquitination. Actually, although polyubiquitination by FBXL5 takes place in the nucleus, Snail1 is degraded in the cytosol. Finally, FBXL5 is highly sensitive to stress conditions and is downregulated by iron depletion and γ-irradiation, explaining Snail1 stabilization in these conditions. These results characterize a novel nuclear ubiquitin ligase controlling Snail1 protein stability and provide the molecular basis for understanding how radiotherapy upregulates the epithelial to mesenchymal transition-inducer Snail1.
authors.affiliation: Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Parc de Recerca Biomèdica de Barcelona, Doctor Aiguader, 88, E-08003, Barcelona, Spain, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain, BRIGHT Institute, Washington University, St. Louis, MO 63110 USA, Departments of Cell Biology and Physiology, Washington University, St. Louis, MO 63110 USA and Department of Medicine, Washington University, St. Louis, MO 63110 USA.
authors.forename: Rosa
authors.initials: R
authors.lastname: Viñas-Castells
authors.forename: Álex
authors.initials: Á
authors.lastname: Frías
authors.forename: Estefanía
authors.initials: E
authors.lastname: Robles-Lanuza
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Longmore
authors.forename: Antonio
authors.initials: A
authors.lastname: García de Herreros
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Díaz
mesh_terms: D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology* / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D044783:F-Box Proteins / Q000378:metabolism*; D005720:Gamma Rays; D006801:Humans; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D055550:Protein Stability; D034741:RNA, Small Interfering; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D044783:F-Box Proteins; C521741:FBXL5 protein, human; D034741:RNA, Small Interfering; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D004247:DNA; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases