| Summary: | 碩士 === 國立臺灣大學 === 分子醫學研究所 === 94 === RNA helicases are involved in many aspects of RNA metabolism including pre-mRNA splicing and mRNA export, decay and translation. We recently found that the mRNA export receptor, TAP, interacted with RNA helicase DDX3, consistence with the role of DDX3 orthologs in mRNA export and translation. To study the function of human DDX3 in mRNA biogenesis, we set out to search for its mRNA targets by using the immunoprecipitation-differential display strategy. We obtained 10 mRNA candidates and found that two of them, FBX22 and SHINC-2 mRNAs, were associated with DDX3 but, however, also bound to other mRNA export-related proteins. We further found that the helicase SAT domain of DDX3 was required for its association with mRNAs. Under cell stress conditions, DDX3 was targeted to the cytoplasmic stress granules (SGs) (Lai and Tarn, unpublished data), and its association with mRNAs was also disrupted. To examine whether DDX3 participates in translation control, we characterized translation complex assembly in the presence of overexpressed DDX3. The results showed that overexpression of DDX3 could interfere with the association of its mRNA ligands with polyribosomes. Therefore, DDX3 might play a role in translation inhibition.
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