Molecular Interrogation of DEAD-box Protein 6

Well-tuned gene expression is essential for life and is in part secured by the post-transcriptional regulators. DEAD-box protein 6 (DDX6) is one such regulator. DDX6 is best known for its participation in RNA turnover and translational repression. In this study, we focus on the roles of DDX6 in regulating gene expression and on the subcellular localization of DDX6, and its regulation, as well as its functional implications. In the first chapter, we elaborated a logical sequence to locate the niche of DDX6 in the context of gene expression and regulation. On this basis, we further expounded the fundamental biochemical properties of DDX6, its functional roles in the cells, and their phenotypic consequences. The second chapter includes our investigation on the governing mechanism of the nucleocytoplasmic distribution of DDX6. We scrutinized the working hypothesis and refuted it with molecular and structural evidence. We further demonstrated that two parallel mechanisms direct the nucleocytoplasmic distribution of DDX6. The third chapter includes our investigation on the regulation of gene expression by DDX6. We adopted an integrative functional genomics approach to investigate the size and the extent of the DDX6-mediated regulation on RNA and protein expression. We first demonstrated that DDX6 binds both the messenger RNA and the long noncoding RNA. In contrast our original expectation, we did not observe significant regulation over the RNA or the protein expression levels by DDX6 in the HeLa cell line. Notwithstanding, we provided evidence that DDX6 regulates gene expression noise. Thus, our results provide a new perspective on the gene regulation by DDX6. The fourth chapter includes the further experimental results related to the nuclear entry mechanism of DDX6. The results described therein may guide further investigations in the future.