Abstract 4403: SMYD2-mediated lysine methylation regulates nuclear transport of beta-catenin in human cancer cells

Abstract

Abstract The canonical Wnt-signal pathway is a major signaling system in cancer cells as well as stem/progenitor cells. It is well-known that binding of Wnt molecules to cell surface receptors, including a Frizzled (Fz) protein and LDL receptor-related protein 6, initiates a transduction cascade leading to stabilization of the transcription coactivator β-catenin, which then enters the nucleus to form a transcriptional complex with T cell factor (TCF) or lymphoid enhancer factor (LEF) to activate the expression of TCF/LEF downstream genes, such as cyclin D1 (CCND1) and c-Myc. However, the molecular mechanisms that regulate nuclear localization of β-catenin and its transcriptional activation are not fully understood. Here we demonstrate that the protein lysine methyltransferase SMYD2 methylates β-catenin at lysine 133, which is located in an amino-terminal domain (NTD), and regulates nuclear transport of β-catenin. After treatment with SMYD2-specific siRNAs in hepatocellular carcinoma SNU475 and SNU449 cells, we fractionated cell components and conducted western blot analysis and found that nuclear localization of β-catenin was significantly decreased after knockdown of SMYD2; we also confirmed this result by immunocytochemistry. In addition, we prepared a lysine 133-substituted β-catenin mutant expression vector and transfected it into 293T cells with a SMYD2 expression vector. We observed that protein amount of lysine 133-substituted β-catenin in the nucleus is significantly lower than that of wild-type β-catenin by western-blot and immunocytochemical analyses. These results indicate that SMYD2-mediated methylation plays a critical role in the nuclear transport of β-catenin in cancer cells. This is a novel mechanism of the canonical Wnt-signal pathway regulated by lysine methylation. Citation Format: Xiaolan Deng, Yusuke Nakamura, Ryuji Hamamoto. SMYD2-mediated lysine methylation regulates nuclear transport of beta-catenin in human cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4403.