title: The novel PIAS-like protein hZimp10 enhances Smad transcriptional activity.
abstract: Transforming growth factor beta (TGF-beta) plays critical roles in the control of cell proliferation, differentiation, and apoptosis. Smad proteins are substrates of the TGF-beta type I receptor and are responsible for transducing receptor signals to target genes in the nucleus. The PIAS (protein inhibitor of activated STAT) proteins were originally identified as transcriptional co-regulators of the JAK-STAT pathway. Subsequently, cross-talk between the PIAS proteins and other signaling pathways has been shown to be involved in various cellular processes. Importantly, PIAS proteins modulate TGF-beta signaling by regulating the transcriptional activity of Smad3. In this study we tested whether hZimp10, a novel PIAS-like protein, acts as other PIAS proteins to regulate Smad3-mediated transcription. We show that expression of exogenous hZimp10 enhances the transcriptional activity of Smad3, which appears to be Smad4-dependent and responsive to TGF-beta induction. Furthermore, knockdown of endogenous hZimp10 reduced the transcriptional activity of Smad3. A protein-protein interaction between Smad3 and Smad4 with hZimp10 was identified in glutathione S-transferase-pulldown and co-immunoprecipitation assays. The Miz domain of hZimp10 and the MH2 domains of Smad3 and Smad4 were mapped as the regions responsible for binding. Results from immunostaining assays further demonstrated that Smad3, Smad4, and hZimp10 co-localize within cell nuclei. Finally, we demonstrated that Smad3/4-mediated transcription is significantly impaired in response to TGF-beta induction in Zimp10 null (zimp10-/-) embryonic fibroblasts. Taken together, these results provide the first line of evidence to demonstrate a role for Zimp10 in regulating the TGF-beta/Smad signaling pathway.
authors.affiliation: Department of Urology, Stanford University School of Medicine, Stanford, California 94303-5118, USA.
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Li
authors.forename: Gregory
authors.initials: G
authors.lastname: Thyssen
authors.forename: Jason
authors.initials: J
authors.lastname: Beliakoff
authors.forename: Zijie
authors.initials: Z
authors.lastname: Sun
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology; D050828:Protein Inhibitors of Activated STAT / Q000502:physiology*; D017434:Protein Structure, Tertiary; D051900:Smad3 Protein / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D051901:Smad4 Protein / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers / Q000502:physiology
chemical_list: D009687:Nuclear Proteins; D050828:Protein Inhibitors of Activated STAT; D051900:Smad3 Protein; D051901:Smad4 Protein; D014157:Transcription Factors; C480599:ZMIZ1 protein, human; C485521:Miz1 protein, mouse; D044767:Ubiquitin-Protein Ligases