title: USP15 is a deubiquitylating enzyme for receptor-activated SMADs.
abstract: The TGFβ pathway is critical for embryonic development and adult tissue homeostasis. On ligand stimulation, TGFβ and BMP receptors phosphorylate receptor-activated SMADs (R-SMADs), which then associate with SMAD4 to form a transcriptional complex that regulates gene expression through specific DNA recognition. Several ubiquitin ligases serve as inhibitors of R-SMADs, yet no deubiquitylating enzyme (DUB) for these molecules has so far been identified. This has left unexplored the possibility that ubiquitylation of R-SMADs is reversible and engaged in regulating SMAD function, in addition to degradation. Here we identify USP15 as a DUB for R-SMADs. USP15 is required for TGFβ and BMP responses in mammalian cells and Xenopus embryos. At the biochemical level, USP15 primarily opposes R-SMAD monoubiquitylation, which targets the DNA-binding domains of R-SMADs and prevents promoter recognition. As such, USP15 is critical for the occupancy of endogenous target promoters by the SMAD complex. These data identify an additional layer of control by which the ubiquitin system regulates TGFβ biology.
authors.affiliation: Department of Medical Biotechnologies, Section of Histology and Embryology, University of Padua, viale G. Colombo 3, 35100 Padua, Italy.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Inui
authors.forename: Andrea
authors.initials: A
authors.lastname: Manfrin
authors.forename: Anant
authors.initials: A
authors.lastname: Mamidi
authors.forename: Graziano
authors.initials: G
authors.lastname: Martello
authors.forename: Leonardo
authors.initials: L
authors.lastname: Morsut
authors.forename: Sandra
authors.initials: S
authors.lastname: Soligo
authors.forename: Elena
authors.initials: E
authors.lastname: Enzo
authors.forename: Stefano
authors.initials: S
authors.lastname: Moro
authors.forename: Simona
authors.initials: S
authors.lastname: Polo
authors.forename: Sirio
authors.initials: S
authors.lastname: Dupont
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Cordenonsi
authors.forename: Stefano
authors.initials: S
authors.lastname: Piccolo
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001665:Binding Sites; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D009865:Oocytes; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D051901:Smad4 Protein / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D064570:Ubiquitin-Specific Proteases; D054875:Ubiquitination; D014981:Xenopus
chemical_list: D055396:Bone Morphogenetic Protein 2; D011993:Recombinant Fusion Proteins; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; D053773:Transforming Growth Factor beta1; D004247:DNA; D010450:Endopeptidases; C579226:USP15 protein, human; D064570:Ubiquitin-Specific Proteases