title: Critical roles of RNA helicase DDX3 and its interactions with eIF4E/PABP1 in stress granule assembly and stress response.
abstract: Upon environmental insults, SGs (stress granules) aid cell survival by serving as sites of translational silencing. RNA helicase DDX3 was reported to associate with SGs. However, its role in SG physiology remains undefined. We have demonstrated previously that DDX3 acts as an eIF4E (eukaryotic initiation factor 4E)-inhibitory protein to suppress translation. In the present study, we indentified the SG marker PABP1 [poly(A)-binding protein 1] as another direct interaction partner of DDX3. We established various stimuli as novel stressors that direct DDX3 with eIF4E and PABP1 into SGs, but not to processing bodies. Interestingly, down-regulation of DDX3 interfered with SG assembly, led to nuclear accumulation of PABP1 and reduced cell viability following stress. Conversely, supplementation with a shRNA (short hairpin RNA)-resistant DDX3 restored SG formation, the translocation of PABP1 into SGs and cell survival. Notably, the SG-inducing capacity of DDX3 is independent of its ATPase and helicase activities, but mapped to the eIF4E-binding region. Moreover, the eIF4E-binding-defective mutant DDX3 was impaired in its SG-inducing ability and protective effect on cell survival under adverse conditions. All together, the present study has characterized DDX3 as a pivotal SG-nucleating factor and illustrates co-ordinative roles for DDX3, eIF4E and PABP1 in integrating environmental stress with translational regulation.
authors: Institute of Biochemistry and Molecular Biology, National Yang Ming University, Taipei 112, Taiwan.
authors: Jing-Wen
authors: JW
authors: Shih
authors: Wei-Ting
authors: WT
authors: Wang
authors: Tsung-Yuan
authors: TY
authors: Tsai
authors: Chu-Yun
authors: CY
authors: Kuo
authors: Hao-Kang
authors: HK
authors: Li
authors: Yan-Hwa
authors: YH
authors: Wu Lee
mesh_terms: D000251:Adenosine Triphosphatases; D017209:Apoptosis / Q000502:physiology; D018053:Arsenites; D045744:Cell Line, Tumor; D002470:Cell Survival; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D039122:Poly(A)-Binding Protein I / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D021381:Protein Transport; D013012:Sorbitol
chemical_list: D018053:Arsenites; D039561:Eukaryotic Initiation Factor-4E; D039122:Poly(A)-Binding Protein I; D013012:Sorbitol; D000251:Adenosine Triphosphatases; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases; C015001:arsenite