SMYD3 links lysine methylation of MAP3K2 to Ras-driven cancer

Abstract

Deregulation in lysine methylation signaling has emerged as a common etiologic factor in cancer pathogenesis, with inhibitors of several histone lysine methyl transferases (KMTs) being developed as chemotherapeutics ¹ . The largely cytoplasmic KMT SMYD3 (SET and MYND domain containing protein 3) is overexpressed in numerous human tumors ^{2- 4} . However, the molecular mechanism by which SMYD3 regulates cancer pathways and its relationship to tumorigenesis in vivo are largely unknown. Here we show that methylation of MAP3K2 by SMYD3 increases MAP Kinase signaling and promotes the formation of Ras-driven carcinomas. Using mouse models for pancreatic ductal adenocarcinoma (PDAC) and lung adenocarcinoma (LAC), we found that abrogating SMYD3 catalytic activity inhibits tumor development in response to oncogenic Ras. We employed protein array technology to identify the MAP3K2 kinase as a target of SMYD3. In cancer cell lines, SMYD3-mediated methylation of MAP3K2 at lysine 260 potentiates activation of the Ras/Raf/MEK/ERK signaling module. Finally, the PP2A phosphatase complex, a key negative regulator of the MAP Kinase pathway, binds to MAP3K2 and this interaction is blocked by methylation. Together, our results elucidate a new role for lysine methylation in integrating cytoplasmic kinase-signaling cascades and establish a pivotal role for SMYD3 in the regulation of oncogenic Ras signaling.