title: Interleukin-1 activates synthesis of interleukin-6 by interfering with a KH-type splicing regulatory protein (KSRP)-dependent translational silencing mechanism.
abstract: Post-transcriptional mechanisms play an important role in the control of inflammatory gene expression. The heterogeneous nuclear ribonucleoprotein K homology (KH)-type splicing regulatory protein (KSRP) triggers rapid degradation of mRNAs for various cytokines, chemokines, and other inflammation-related proteins by interacting with AU-rich elements (AREs) in the 3'-untranslated mRNA regions. In addition to destabilizing mRNAs, AU-rich elements can restrict their translation. Evidence that KSRP also participates in translational silencing was obtained in a screen comparing the polysome profiles of cells with siRNA-mediated depletion of KSRP with that of control cells. Among the group of mRNAs showing increased polysome association upon KSRP depletion are those of interleukin (IL)-6 and IL-1α as well as other ARE-containing transcripts. Redistribution of IL-6 mRNA to polysomes was associated with increased IL-6 protein secretion by the KSRP-depleted cells. Silencing of IL-6 and IL-1α mRNAs depended on their 3'-untranslated regions. The sequence essential for translational control of IL-6 mRNA and its interaction with KSRP was located to an ARE. KSRP-dependent silencing was reversed by IL-1, a strong inducer of IL-6 mRNA and protein expression. The results identify KSRP as a protein involved in ARE-mediated translational silencing. They suggest that KSRP restricts inflammatory gene expression not only by enhancing degradation of mRNAs but also by inhibiting translation, both functions that are counteracted by the proinflammatory cytokine IL-1.
authors.affiliation: Institute of Biochemistry, Medical School Hannover, D-30623 Hannover, Germany.
authors.forename: Sonam
authors.initials: S
authors.lastname: Dhamija
authors.forename: Nancy
authors.initials: N
authors.lastname: Kuehne
authors.forename: Reinhard
authors.initials: R
authors.lastname: Winzen
authors.forename: Anneke
authors.initials: A
authors.lastname: Doerrie
authors.forename: Oliver
authors.initials: O
authors.lastname: Dittrich-Breiholz
authors.forename: Basant Kumar
authors.initials: BK
authors.lastname: Thakur
authors.forename: Michael
authors.initials: M
authors.lastname: Kracht
authors.forename: Helmut
authors.initials: H
authors.lastname: Holtmann
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D020856:AT Rich Sequence; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D053582:Interleukin-1alpha / Q000235:genetics / Q000378:metabolism*; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000096:biosynthesis*; D012270:Ribosomes / Q000378:metabolism; D015534:Trans-Activators / Q000096:biosynthesis* / Q000172:deficiency
chemical_list: D020413:3' Untranslated Regions; C508600:IL6 protein, human; D053582:Interleukin-1alpha; D015850:Interleukin-6; C105789:KHSRP protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D015534:Trans-Activators