Spatial Regulation of Argonaute in Mammalian RNA Interference

Abstract

RNA interference (RNAi) is mediated by microRNAs and Argonaute (AGO) proteins. AGO:miRNA complexes regulate gene expression by targeting messenger RNAs for degradation or by suppressing its translation. RNAi was perceived to take place in the cytoplasm of cells and regulate only mature RNAs. However, recently, the RNAi pathway in humans is no longer considered solely a cytoplasmic event, since the discovery of nuclear localization of AGO proteins. In this thesis, we show that the translocation of AGO2 into the nucleus affects the canonical RNAi function. In paper I and IV, we demonstrate that nuclear AGO2 is associated with cancer aggressiveness, particularly in neuroblastoma. Moreover, nuclear AGO2 is observed in virus-infected cells in paper II. By blocking the nuclear localization of AGO2 and forcing its expression in the cytoplasm, cancer cell proliferation and viral replication are significantly reduced. Our findings suggest a potential therapeutic strategy for viral infections and cancer treatment by preventing AGO2 nuclear translocation. Lastly, we develop RBProximity-CLIP to investigate AGO-RNA interactions at subcellular level in paper III.