Protein arginine methyltransferase 1 is a novel regulator of MYCN in neuroblastoma

// Allison Eberhardt 1 , Jeanne N. Hansen 1 , Jan Koster 2 , Louis T. Lotta Jr. 1 , Simeng Wang 1 , Emmett Livingstone 1 , Kun Qian 3 , Linda J. Valentijn 2 , Yujun George Zheng 3 , Nina F. Schor 1 , Xingguo Li 1 1 Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642, USA 2 Department of Oncogenomics, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands 3 Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, Georgia 30602, USA Correspondence to: Nina F. Schor, email: Nina_schor@urmc.rochester.edu Xingguo Li, email: Xingguo_li@urmc.rochester.edu Keywords: neuroblastoma, MYCN, PRMT1, arginine methylation, protein stability Received: April 30, 2016      Accepted: August 13, 2016      Published: August 23, 2016 ABSTRACT Amplification or overexpression of MYCN is associated with poor prognosis of human neuroblastoma. We have recently defined a MYCN-dependent transcriptional signature, including protein arginine methyltransferase 1 (PRMT1), which identifies a subgroup of patients with high-risk disease. Here we provide several lines of evidence demonstrating PRMT1 as a novel regulator of MYCN and implicating PRMT1 as a potential therapeutic target in neuroblastoma pathogenesis. First, we observed a strong correlation between MYCN and PRMT1 protein levels in primary neuroblastoma tumors. Second, MYCN physically associates with PRMT1 by direct protein-protein interaction. Third, depletion of PRMT1 through siRNA knockdown reduced neuroblastoma cell viability and MYCN expression. Fourth, we showed that PRMT1 regulates MYCN stability and identified MYCN as a novel substrate of PRMT1. Finally, we demonstrated that mutation of putatively methylated arginine R65 to alanine decreased MYCN stability by altering phosphorylation at residues serine 62 and threonine 58. These results provide mechanistic insights into the modulation of MYCN oncoprotein by PRMT1, and suggest that targeting PRMT1 may have a therapeutic impact on MYCN-driven oncogenesis.