The role of XPO1 in nuclear export of RNA

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Project Summary The focus of research in the Taylor laboratory is on nuclear export in eukaryotic cells, which we study by perturbing the normal function of the main exporter of proteins, XPO1 or Exportin-1. We use molecular biology, genomics, proteomics, and mouse modeling to determine the mechanisms of XPO1-mediated nuclear export function and the role of XPO1 in disease pathogenesis. We also study how XPO1 interacts with other proteins and molecules such as ribonucleic acid (RNA). In the next five years, the goal of the lab is to define the role of XPO1 in the nuclear export of RNA. The laboratory is currently pursuing the following projects. Defining the molecular effects of wildtype and mutant XPO1 on gene expression, splicing, and translation. Given the known role of XPO1 in the export of small nuclear RNA (snRNA) and ribosomal RNA (rRNA) via the binding of RNA binding proteins, we hypothesize that alterations in XPO1 may impact RNA splicing and/or mRNA translation. We have generated several genetically engineered models to allow endogenous expression of the XPO1 E571K or R749Q mutation, including conditional knockin mice. We have demonstrated through a variety of proteomic, biochemical, structural, and molecular studies that XPO1 E571K affects recognition of its cargo’s nuclear export signal (NES) and results specifically in altered export of of NFκB and NFAT transcription factor proteins. The aim of my first project is to continue to study the extent of how the XPO1 E571K alters nuclear export and to explore whether RNA export, and consequent mRNA splicing and translation, is affected through the mislocalization of RNA binding proteins. We have recently discovered another mutation, XPO1 R749Q, that affects nuclear export by increasing the export of proteins out of the nucleus. We plan to study which proteins this affects and how this affects cell growth, cell cycle and other homeostatic processes. We are also modeling overexpression of XPO1 and will compare how this overactive mutant compares to overexpression in relation to protein and RNA export. Drugs that selectively inhibit XPO1 will allow us to isolate the effects of XPO1- dependent export. Furthermore, our preliminary data show that cells with abnormal splicing due to SF3B1 mutations undergo apoptosis upon exposure to XPO1 inhibitors. We will also investigate the effects of XPO1 inhibition in mutant Sf3b1 expressing cells using genetically engineered cell lines and an Sf3b1 knockin mouse model. We hypothesis that XPO1 inhibition perturbs RNA export and affects gene expression and mRNA splicing given the known role of XPO1 to export small nuclear RNA via RNA-binding proteins. This work will serve as foundational data for future grant submissions investigating the biology of XPO1 and its role in nuclear export of RNA. The overarching goal of this research is aligned with the NIGMS’ mission to support new basic discovery science that can eventually culminate in new medical therapies. By better understanding the role of XPO1 in RNA export, we can better design therapies that modulate nuclear export or RNA splicing for a wide range of diseases where RNA regulation may play a role.