title: MicroRNA-223 regulates cyclin E activity by modulating expression of F-box and WD-40 domain protein 7.
abstract: F-box and WD-40 domain protein 7 (Fbw7) provides substrate specificity for the Skp1-Cullin1-F-box protein (SCF) ubiquitin ligase complex that targets multiple oncoproteins for degradation, including cyclin E, c-Myc, c-Jun, Notch, and mammalian target of rapamycin (mTOR). Fbw7 is a bona fide tumor suppressor, and loss-of-function mutations in FBXW7 have been identified in diverse human tumors. Although much is known about targets of the Fbw7 ubiquitin ligase pathway, relatively little is known about the regulation of Fbw7 expression. We identified a panel of candidate microRNA regulators of Fbw7 expression within a study of gene expression alterations in primary erythroblasts obtained from cyclin E(T74A T393A) knock-in mice, which have markedly dysregulated cyclin E expression. We found that overexpression of miR-223, in particular, significantly reduces FBXW7 mRNA levels, increases endogenous cyclin E protein and activity levels, and increases genomic instability. We next confirmed that miR-223 targets the FBXW7 3'-untranslated region. We then found that reduced miR-223 expression in primary mouse embryonic fibroblasts leads to increased Fbw7 expression and decreased cyclin E activity. Finally, we found that miR-223 expression is responsive to acute alterations in cyclin E regulation by the Fbw7 pathway. Together, our data indicate that miR-223 regulates Fbw7 expression and provide the first evidence that activity of the SCF(Fbw7) ubiquitin ligase can be modulated directly by the microRNA pathway.
authors.affiliation: Department of Medicine, Division of Hematology/Oncology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
authors.forename: Yanfei
authors.initials: Y
authors.lastname: Xu
authors.forename: Tanushri
authors.initials: T
authors.lastname: Sengupta
authors.forename: Lokesh
authors.initials: L
authors.lastname: Kukreja
authors.forename: Alex C
authors.initials: AC
authors.lastname: Minella
mesh_terms: D020413:3' Untranslated Regions / Q000502:physiology*; D000818:Animals; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000235:genetics; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000096:biosynthesis* / Q000235:genetics; D000073979:F-Box-WD Repeat-Containing Protein 7; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D020014:K562 Cells; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D018797:Cell Cycle Proteins; D019927:Cyclin E; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; D035683:MicroRNAs; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D051880:Receptors, Notch; D044843:SKP Cullin F-Box Protein Ligases; D058570:TOR Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; C513273:FBXW7 protein, human; C525067:MIR223, human; C544877:MIRN223 microRNA, mouse; C489427:MYC protein, human; C489428:Myc protein, mouse; C546842:MTOR protein, human
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