WEE1 epigenetically modulates 5-hmC levels by pY37-H2B dependent regulation of IDH2 gene expression

// Nupam P. Mahajan 1, 6 , Pavani Malla 1 , Shambhavi Bhagwat 1 , Vasundhara Sharma 1 , Amod Sarnaik 3 , Jongphil Kim 4, 6 , Shari Pilon-Thomas 5 , Jeffery Weber 7 and Kiran Mahajan 2, 6 1 Department of Drug Discovery, Moffitt Cancer Center, Tampa, FL 33612, USA 2 Department of Tumor Biology, Moffitt Cancer Center, Tampa, FL 33612, USA 3 Department of Cutaneous Oncology, Moffitt Cancer Center, Tampa, FL 33612, USA 4 Department of Biostatistics and Bioinformatics, Moffitt Cancer Center, Tampa, FL 33612, USA 5 Department of Immunology, Moffitt Cancer Center, Tampa, FL 33612, USA 6 Department of Oncological Sciences, University of South Florida, Tampa, FL 33612, USA 7 Laura and Isaac Perlmutter Cancer Center, NYU Langone Medical Center, New York, NY 10016, USA Correspondence to: Nupam P. Mahajan, email: nupam.mahajan@moffitt.org Kiran Mahajan, email: kiran.mahajan@moffitt.org Keywords: WEE1; histone H2B; tyrosine phosphorylation; IDH2; tyrosine kinase Received: April 04, 2017      Accepted: October 25, 2017      Published: November 10, 2017 ABSTRACT Epigenetic signaling networks dynamically regulate gene expression to maintain cellular homeostasis. Previously, we uncovered that WEE1 phosphorylates histone H2B at tyrosine 37 (pY37-H2B) to negatively regulate global histone transcriptional output. Although pY37-H2B is readily detected in cancer cells, its functional role in pathogenesis is not known. Herein, we show that WEE1 deposits the pY37-H2B marks within the tumor suppressor gene, isocitrate dehydrogenase 2 ( IDH2 ), to repress transcription in multiple cancer cells, including glioblastoma multiforme (GBMs), melanoma and prostate cancer. Consistently, GBMs and primary melanoma tumors that display elevated WEE1 mRNA expression exhibit significant down regulation of the IDH2 gene transcription. IDH2 catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG), an essential cofactor for the TET family of 5-methylcytosine (5mC) hydroxylases that convert 5-mC to 5-hydroxymethylcytosine (5-hmC). Significantly, the WEE1 inhibitor AZD1775 not only abrogated the suppressive H2B Y37-phosphorylation and upregulated IDH2 mRNA levels but also effectively reversed the ‘loss of 5-hmC’ phenotype in melanomas, GBMs and prostate cancer cells, as well as melanoma xenograft tumors. These data indicate that the epigenetic repression of IDH2 by WEE1/pY37-H2B circuit may be a hitherto unknown mechanism of global 5-hmC loss observed in human malignancies.