Grant: Project Grant

To express a gene, its DNA must copied into mRNA in the nucleus. This mRNA is then packaged into complexes that contain proteins and known as messenger ribonucleoproteins (mRNPs). These mRNPs are then ferried across the nuclear pore to reach the cytoplasm where they are used by ribosomes to make new proteins. These proteins are functional molecules that impact the development, physiology and homeostasis of the organism. We have uncovered a key step in the gene expression pathway. We have shown that the protein RanBP2, which is part of the nuclear pore, is required for the efficient production of secretory proteins, likely by modifying how mRNAs are packaged into mRNPs. This mRNP maturation event likely impacts how many mRNAs are translated into proteins. Mutations in RanBP2 are associated to Acute Necrotizing Encephalopathy 1 (ANE1), a condition where otherwise normal individuals overproduce cytokines in response to influenza infections. This leads to seizures, coma and a high rate of mortality. Four separate dominant point mutations in RanBP2 have been linked to this disease. In cells that lack RanBP2 or that have mutations that impair its ability to modify other proteins, we find that the cytokine interleukin 6 (IL6) is over-expressed, indicating that RanBP2 likely alters the mRNP that contains the mRNA that is used to make IL6 protein. In this proposal we outline our plans to determine the molecular mechanisms by which RanBP2 regulates mRNP maturation. We have also been in contact with families afflicted by ANE1 and we plan to use epithelial nasal swabs and white blood cells (monocytes) from these patients to understand how mutations in RanBP2 alters cytokine production in normal conditions and after viral infection. Our work will not only provide key insights into the pathology of ANE1, but will also provide a deeper understanding of how RanBP2 regulates the expression of cytokines and other secretory proteins.