Impact of Argonaute 2 (AGO2) PAZ domain mutations on miRNA turnover, target interaction and tumour development

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MicroRNAs (miRNAs) are a conserved class of small RNAs with important roles in the regulation of many cellular and developmental processes. They guide AGO complexes to target mRNAs, and decrease their stability and translation. It has been estimated that miRNAs regulate the expression of ~60% of mRNAs. Misregulation of miRNAs has been linked to disruption of cell homeostasis and tumour development. miRNAs can either promote tumorigenesis or suppress it depending on their target specificity and the context. To date, there is limited knowledge on the regulation of miRNA turnover. Previous work has shown that disrupting critical interactions between the miRNA 3’ end and AGO PAZ domain was sufficient to induce extensive modifications. Those mutations released the miRNA 3’ end from its protective pocket within the PAZ domain making it accessible to tailing and trimming, thus leading to degradation. The aim of our project is to further evaluate the role of AGO PAZ domain mutations in cancer. Based on the previous studies, we hypothesize that mutations of the AGO PAZ domain found in cancer patients may contribute to tumor progression by regulating the abundance of individual miRNAs within the miRNA pool or by altering the binding and repression of target mRNAs. The project will be separated into two main objectives: Objective 1 aims to understand the general impacts of AGO2 PAZ mutations on the miRNA profile and miRNA modification and decay as well as downstream effects. Objective 2 aims to understand the role of AGO2 PAZ mutations in cancer. For this we will create a library of AGO2 PAZ mutants confirmed or likely to occur in cancer patients and analyze their impact on the miRNA pool and cellular behavior. Throughout the project we will combine the analysis of big data sets with techniques of cell biology and RNA and protein biochemistry. Prospectively, our data could be used for identification of new biomarkers or targeted therapy approaches.