title: The major vault protein is responsive to and interferes with interferon-gamma-mediated STAT1 signals.
abstract: The major vault protein (MVP) is the main component of vaults, large ribonucleoprotein particles implicated in the regulation of cellular signaling cascades and multidrug resistance. Here, we identify MVP as an interferon gamma (IFN-gamma)-inducible protein. Treatment with IFN-gamma resulted in a significant upregulation of MVP promoter activity as well as mRNA and protein levels. Activation of MVP expression by IFN-gamma involved transcriptional upregulation through the JAK/STAT pathway based on an interaction of STAT1 with an interferon-gamma-activated site (GAS) within the proximal MVP promoter. Mutation of this site distinctly reduced basal as well as IFN-gamma-stimulated MVP transcription. IFN-gamma also significantly enhanced the translation rate of MVP. Ectopic MVP overexpression in the MVP-negative lung cancer cell model H65 led to a downregulation of three known IFN-gamma-regulated genes, namely ICAM-1, CD13 and CD36. Additionally, presence of MVP in H65 cells blocked both basal and IFN-gamma-induced ICAM-1 expression whereas downmodulation of endogenous MVP levels by shRNA enhanced IFN-gamma-induced ICAM-1 expression in U373 glioblastoma cells. MVP-mediated IFN-gamma insensitivity was accompanied by significantly reduced STAT1 phosphorylation at Y701 and diminished translocation of STAT1 into the nucleus. Summarizing, we identify MVP as an IFN-gamma-responsive gene interfering with IFN-gamma-activated JAK/STAT signals. These data further substantiate that the vault particle functions as a general interaction platform for cellular signaling cascades.
authors.affiliation: Department of Medicine I, Institute of Cancer Research, Medical University Vienna, Borschkegasse 8a, A-1090 Vienna, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Steiner
authors.forename: Klaus
authors.initials: K
authors.lastname: Holzmann
authors.forename: Christine
authors.initials: C
authors.lastname: Pirker
authors.forename: Leonilla
authors.initials: L
authors.lastname: Elbling
authors.forename: Michael
authors.initials: M
authors.lastname: Micksche
authors.forename: Hedwig
authors.initials: H
authors.lastname: Sutterlüty
authors.forename: Walter
authors.initials: W
authors.lastname: Berger
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects; D020394:Vault Ribonucleoprotein Particles / Q000096:biosynthesis* / Q000235:genetics; D000099187:Major Vault Protein
chemical_list: D000970:Antineoplastic Agents; D007371:Interferon-gamma; D050794:STAT1 Transcription Factor; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein; C494079:STAT1 protein, human