title: Ribosomal 18 S RNA processing by the IGF-I-responsive WDR3 protein is integrated with p53 function in cancer cell proliferation.
abstract: Insulin-like growth factor-I (IGF-I) signaling is strongly associated with cell growth and regulates the rate of synthesis of the rRNA precursor, the first and the key stage of ribosome biogenesis. In a screen for mediators of IGF-I signaling in cancer, we recently identified several ribosome-related proteins, including NEP1 (nucleolar essential protein 1) and WDR3 (WD repeat 3), whose homologues in yeast function in ribosome processing. The WDR3 gene and its locus on chromosome 1p12-13 have previously been linked with malignancy. Here we show that IGF-I induces expression of WDR3 in transformed cells. WDR3 depletion causes defects in ribosome biogenesis by affecting 18 S rRNA processing and also causes a transient down-regulation of precursor rRNA levels with moderate repression of RNA polymerase I activity. Suppression of WDR3 in cells expressing functional p53 reduced proliferation and arrested cells in the G(1) phase of the cell cycle. This was associated with activation of p53 and sequestration of MDM2 by ribosomal protein L11. Cells lacking functional p53 did not undergo cell cycle arrest upon suppression of WDR3. Overall, the data indicate that WDR3 has an essential function in 40 S ribosomal subunit synthesis and in ribosomal stress signaling to p53-mediated regulation of cell cycle progression in cancer cells.
authors.affiliation: Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, University College Cork, Cork, Ireland.
authors.forename: Mary
authors.initials: M
authors.lastname: McMahon
authors.forename: Verónica
authors.initials: V
authors.lastname: Ayllón
authors.forename: Kostya I
authors.initials: KI
authors.lastname: Panov
authors.forename: Rosemary
authors.initials: R
authors.lastname: O'Connor
mesh_terms: D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D009369:Neoplasms / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D012337:RNA, Ribosomal, 18S; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C120702:WDR3 protein, human; D007334:Insulin-Like Growth Factor I; C549212:EMG1 protein, human; D008780:Methyltransferases
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