Grant: Project Grant

Gene expression begins in the nucleus, where DNA is transcribed to mRNA, which is processed and packaged into large RNA-protein assemblies called messenger ribonucleoprotein (mRNP) complexes. These mRNPs are then transported from the nucleus to the cytoplasm through the nuclear pore. Then in the cytoplasm, these mRNAs are translated into proteins to complete the gene expression pathway. At each step in this pathway, the proteins in the mRNPs are modified, added or removed, in what are known as "mRNP remodelling events". One key remodelling event occurs just after the mRNP emerges from the nuclear pore by the RanBP2/Nup358 protein. RanBP2 sits on the cytoplasmic face of the pore, and can attach the small SUMO peptide to proteins in the mRNP and influence how the packaged mRNA is translated. We have found that RanBP2 is required to suppress the expression of cytokine mRNAs, but it is unclear if this is due to mRNP remodelling at the pore. Mutations in RanBP2 cause Acute Necrotizing Encephalopathy (ANE), a rare pediatric disease where healthy individuals secrete excessive cytokines in response to respiratory infection. This leads to seizures, coma, and either long lasting neuropathy or, in the worst-case scenario, death. It is unclear how these mutations affect mRNP maturation. In this proposal we outline out our plans to determine: 1) Whether RanBP2 must be anchored to the nuclear pore to promote mRNP remodelling. 2) What mRNAs are affected by RanBP2 and how it alters their mRNP composition. 3) How ANE mutations impact mRNA translation and innate immune signalling in virus-infected cells isolated from patients. Our work will help to uncover how RanBP2 orchestrates changes in how cells translate mRNAs and modulate innate immune pathways in response to viral infection. This work will lead to new therapeutics to treat not only disease such as ANE, but also other conditions that are caused by the acute over-activation of the innate immune response.