Elucidating the Role of RanBP2/Nup358 in the Regulation of Cytokines mRNAs

RanBP2 is a small ubiquitin-like modifier (SUMO) E3-ligase located at the cytoplasmic filaments of the nuclear pore complex, and is also present at low levels in the cytosol. Mutations in RanBP2 are linked to acute necrotizing encephalopathy 1 (ANE1), a rare pediatric disorder marked by excessive cytokine production upon viral infection. While RanBP2 has been shown to enhance translation of certain secretory and membrane-bound proteins, its role in cytokine regulation and how ANE1-associated mutations affect this function remain unclear. Using CRISPR-engineered cell lines, we demonstrated that RanBP2-mediated SUMOylation is essential for the translational repression of interleukin 6 (IL6) and tumor necrosis factor α (TNFα) mRNAs, which encode for two cytokines prominently upregulated in ANE1. We showed that RanBP2 SUMOylates Argonaute (AGO) proteins, enhancing their interaction with target mRNAs and their binding partner GW182 to promote miRNA-mediated silencing of cytokine mRNAs. This repression depends on RanBP2’s localization at the nuclear pore, supporting a model in which RanBP2 regulates gene expression by modulating mRNP maturation upon their nuclear export. Proteomic analyses further revealed that ANE1-associated mutations alter RanBP2’s interactome. These mutations disrupt RanBP2’s interaction with immune repressors such as PP6, while enhancing its association with anti-viral proteins such as TRIM5α. Such changes may contribute to the dysregulated immune response seen in ANE1 patients. In addition, we uncovered a novel role for RanBP2 in stress granule dynamics. We showed that RanBP2 SUMOylates G3BP2, a core stress granule component, to delay stress granule formation during stress and promote their disassembly during recovery. Since many viruses target stress granules to evade immune response, this finding implicates RanBP2 in an additional layer of immune regulation during viral infection. Together, our findings establish RanBP2 as a key regulator of cytokine expression and innate immunity. This work provides a biochemical framework for how RanBP2 modulates cytokine expression, and offers new mechanistic insights into how mutations in RanBP2 contribute to hyperinflammation in ANE1.

Department dc:contributor.department

Biochemistry

Year dc:date.issued

2025

Author dc:creator

• Wang, Yifan

Advisor dc:contributor.advisor

• Palazzo, Alexander F

• Acute Necrotizing Encephalopathy Type 1
• Argonaute
• Cytokine
• Interleukin 6
• mRNP maturation
• Nuclear pore

Handle dc:identifier.uri

https://hdl.handle.net/1807/150357

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/150357