title: Novel role for molecular transporter importin 9 in posttranscriptional regulation of IFN-ε expression.
abstract: IFN-ε is a unique type I IFN whose constitutive expression in lung, brain, small intestine, and reproductive tissues is only partially understood. Our previous observation that posttranscriptional events participate in the regulation of IFN-ε mRNA expression led us to investigate whether the 5' and/or 3' untranslated regions (UTR) have regulatory functions. Surprisingly, we found that full-length IFN-ε 5'UTR markedly suppressed mRNA expression under basal conditions. Analysis of the secondary structure of this region predicted formation of two stable stem-loop structures, loops 1 and 2. Studies using luciferase constructs harboring various stretches of IFN-ε 5'UTR and mutant constructs in which the conformation of loop structures was disrupted showed that loop 1 is essential for regulation of mRNA expression. Incubation of HeLa cell extracts with agarose-bound RNAs harboring IFN-ε loop structures identified importin 9 (IPO9), a molecular transporter and chaperone, as a candidate that associates with these regions of the 5'UTR. IPO9 overexpression decreased, and IPO9 silencing increased basal IFN-ε expression. Our studies uncover a previously undescribed function for IPO9 as a specific, and negative, posttranscriptional regulator of IFN-ε expression, and they identify key roles for IFN-ε stem-loop structure 1 in this process. IPO9-mediated effects on 5'UTRs appear to extend to additional mRNAs, including hypoxia-inducible factor-1α, that can form specific loop structures.
authors.affiliation: Department of Vascular Biology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan. tomo1027@cc.hirosaki-u.ac.jp
authors.forename: Tomoh
authors.initials: T
authors.lastname: Matsumiya
authors.forename: Fei
authors.initials: F
authors.lastname: Xing
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ebina
authors.forename: Ryo
authors.initials: R
authors.lastname: Hayakari
authors.forename: Tadaatsu
authors.initials: T
authors.lastname: Imaizumi
authors.forename: Hidemi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kikuchi
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Topham
authors.forename: Kei
authors.initials: K
authors.lastname: Satoh
authors.forename: Diana M
authors.initials: DM
authors.lastname: Stafforini
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D016384:Consensus Sequence; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D007372:Interferons / Q000096:biosynthesis / Q000235:genetics*; D055029:Inverted Repeat Sequences / Q000235:genetics*; D028884:Karyopherins / Q000235:genetics / Q000502:physiology*; D008322:Mammals / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D034622:RNA Interference; D020871:RNA Stability; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D002583:Uterine Cervical Neoplasms / Q000473:pathology
chemical_list: D020121:5' Untranslated Regions; C524005:IFNE protein, human; C587011:IPO9 protein, human; D028884:Karyopherins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D007372:Interferons