title: Interferon-dependent engagement of eukaryotic initiation factor 4B via S6 kinase (S6K)- and ribosomal protein S6K-mediated signals.
abstract: Although the roles of Jak-Stat pathways in type I and II interferon (IFN)-dependent transcriptional regulation are well established, the precise mechanisms of mRNA translation for IFN-sensitive genes remain to be defined. We examined the effects of IFNs on the phosphorylation/activation of eukaryotic translation initiation factor 4B (eIF4B). Our data show that eIF4B is phosphorylated on Ser422 during treatment of sensitive cells with alpha IFN (IFN-alpha) or IFN-gamma. Such phosphorylation is regulated, in a cell type-specific manner, by either the p70 S6 kinase (S6K) or the p90 ribosomal protein S6K (RSK) and results in enhanced interaction of the protein with eIF3A (p170/eIF3A) and increased associated ATPase activity. Our data also demonstrate that IFN-inducible eIF4B activity and IFN-stimulated gene 15 protein (ISG15) or IFN-gamma-inducible chemokine CXCL-10 protein expression are diminished in S6k1/S6k2 double-knockout mouse embryonic fibroblasts. In addition, IFN-alpha-inducible ISG15 protein expression is blocked by eIF4B or eIF3A knockdown, establishing a requirement for these proteins in mRNA translation/protein expression by IFNs. Importantly, the generation of IFN-dependent growth inhibitory effects on primitive leukemic progenitors is dependent on activation of the S6K/eIF4B or RSK/eIF4B pathway. Taken together, our findings establish critical roles for S6K and RSK in the induction of IFN-dependent biological effects and define a key regulatory role for eIF4B as a common mediator and integrator of IFN-generated signals from these kinases.
authors.affiliation: Robert H. Lurie Comprehensive Cancer Center and and Division of Hematology-Oncology, Northwestern University Medical School, Chicago, IL 60611, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Kroczynska
authors.forename: Surinder
authors.initials: S
authors.lastname: Kaur
authors.forename: Efstratios
authors.initials: E
authors.lastname: Katsoulidis
authors.forename: Beata
authors.initials: B
authors.lastname: Majchrzak-Kita
authors.forename: Antonella
authors.initials: A
authors.lastname: Sassano
authors.forename: Sara C
authors.initials: SC
authors.lastname: Kozma
authors.forename: Eleanor N
authors.initials: EN
authors.lastname: Fish
authors.forename: Leonidas C
authors.initials: LC
authors.lastname: Platanias
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D039642:Eukaryotic Initiation Factors; D016898:Interferon-alpha; D034741:RNA, Small Interfering; C031799:eIF-4B; D007371:Interferon-gamma; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038744:Ribosomal Protein S6 Kinases, 90-kDa