Protein-RNA interactions in cancer - PROJECT SUMMARY/ ABSTRACT Protein-RNA interactions underlie an important and understudied component of gene regulation. RNA-binding proteins carry out numerous functions relating to the production, splicing, processing, and stability of mRNA molecules. A few years ago, we discovered that the oncofetal RNA binding protein, IGF2BP3, binds to the 3’ untranslated region of mRNA and regulates mRNA stability via a mechanism that involves the RNA-induced silencing complex. In more recent work, we found that IGF2BP3 also binds near 3’-splice sites, and may regulate alternative splicing. Together, our findings suggest dual roles in mRNA regulation for IGF2BP3. IGF2BP3 regulates genes that are related to proliferation, migration, and signaling- which are important in fetal development- but also in cancer. Concordant with this gene regulatory function, IGF2BP3 is overexpressed in a wide range of malignancies, including acute leukemia, and portends a poor prognosis when highly expressed. Using novel, murine genetic models of IGF2BP3 deficiency, we have now discovered that IGF2BP3 is required for the development of a fully-penetrant, lethal leukemia in vivo. Together, our extensive prior work, both published and unpublished, provides a mechanistic framework for its function, and a solid foundation for the importance of this protein in disease. To fully understand the nature of these protein-RNA interactions and to understand their role in cancer, we propose two aims. In the first aim, we will carefully delineate the mechanism underlying IGF2BP3 function by a combination of carefully executed experiments (Aim 1). In the second aim, we will characterize the importance of IGF2BP3 in leukemia initiation, propagation and maintenance using a set of carefully constructed genetic models and gene editing in primary cells. Next, we will characterize how the two proposed gene regulatory mechanisms- RNA stability and pre-mRNA splicing- play roles in cancer initiation, using a combination of reverse genetics, miRNA regulation, and isoform specific expression. Together, this work will lead to a layered, detailed understanding of how mechanistic basis of protein-RNA interactions is intimately connected to gene expression deregulation and the malignant transformation of cells. Importantly, it will pave the way to develop novel diagnostic and therapeutic approaches in malignancies characterized by massive transcriptomic dysregulation underpinned by alterations of RNA-binding proteins.
