title: DDX3 regulates cell growth through translational control of cyclin E1.
abstract: DDX3 belongs to the DEAD box family of RNA helicases, but the details of its biological function remain largely unclear. Here we show that knockdown of DDX3 expression impedes G(1)/S-phase transition of the cell cycle. To know how DDX3 may act in cell cycle control, we screened for cellular mRNA targets of DDX3. Many of the identified DDX3 targets encoded cell cycle regulators, including G(1)/S-specific cyclin E1. DDX3 depletion specifically downregulates translation of cyclin E1 mRNA. Moreover, our data suggest that DDX3 participates in translation initiation of targeted mRNAs as well as in cell growth control via its RNA helicase activity. Consistent with these findings, we show that in the temperature-sensitive DDX3 mutant hamster cell line tsET24, cyclin E1 expression is downregulated at a nonpermissive temperature that inactivates mutant DDX3. Taken together, our results indicate that DDX3 is critical for translation of cyclin E1 mRNA, which provides an alternative mechanism for regulating cyclin E1 expression during the cell cycle.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, 128 Academy Road Section 2, Nankang, Taipei 11529, Taiwan.
authors.forename: Ming-Chih
authors.initials: MC
authors.lastname: Lai
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Chang
authors.forename: Sheau-Yann
authors.initials: SY
authors.lastname: Shieh
authors.forename: Woan-Yuh
authors.initials: WY
authors.lastname: Tarn
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism*; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006801:Humans; D009154:Mutation; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; C475820:CCNE1 protein, human; D019927:Cyclin E; D015513:Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases