title: Identification of DHX33 as a mediator of rRNA synthesis and cell growth.
abstract: In this report, we employed a lentiviral RNA interference screen to discover nucleolar DEAD/DEAH-box helicases involved in RNA polymerase I (Pol I)-mediated transcriptional activity. Our screen identified DHX33 as an important modulator of 47S rRNA transcription. We show that DHX33 is a cell cycle-regulated nucleolar protein that associates with ribosomal DNA (rDNA) loci, where it interacts with the RNA Pol I transcription factor upstream binding factor (UBF). DHX33 knockdown decreased the association of Pol I with rDNA and caused a dramatic decrease in levels of rRNA synthesis. Wild-type DHX33 overexpression, but not a DNA binding-defective mutant, enhanced 47S rRNA synthesis by promoting the association of RNA polymerase I with rDNA loci. In addition, an NTPase-defective DHX33 mutant (K94R) acted as a dominant negative mutant, inhibiting endogenous rRNA synthesis. Moreover, DHX33 deficiency in primary human fibroblasts triggered a nucleolar p53 stress response, resulting in an attenuation of proliferation. Thus, we show the mechanistic importance of DHX33 in rRNA transcription and proliferation.
authors.affiliation: BRIGHT Institute, Department of Internal Medicine, Division of Molecular Oncology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Yandong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jason T
authors.initials: JT
authors.lastname: Forys
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Miceli
authors.forename: Abigail S
authors.initials: AS
authors.lastname: Gwinn
authors.forename: Jason D
authors.initials: JD
authors.lastname: Weber
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints; D002466:Cell Nucleolus / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D009697:Nucleolus Organizer Region / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism; D061251:Primary Cell Culture; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D034622:RNA Interference; D012318:RNA Polymerase I / Q000378:metabolism; D012335:RNA, Ribosomal / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D035463:Pol1 Transcription Initiation Complex Proteins; D021122:Protein Subunits; D012335:RNA, Ribosomal; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C063844:transcription factor UBF; D012318:RNA Polymerase I; C568925:DHX33 protein, human; D053487:DEAD-box RNA Helicases