At sites of chronic inflammation epithelial cells undergo aberrant DNA methylation that contributes to tumorigenesis. Inflammation is associated with an increase in reactive oxygen species (ROS) that cause oxidative DNA damage, which has also been linked to epigenetic alterations. We previously demonstrated that in response to ROS, mismatch repair proteins MSH2 and MSH6 recruit epigenetic silencing proteins DNA methyltransferase 1 (DNMT1) and polycomb repressive complex 2 (PRC2) members to sites of DNA damage, resulting in transcriptional repression of tumor suppressor genes (TSGs). However, it was unclear what signal is unique to ROS that results in the chromatin binding of MSH2 and MSH6. Herein, we demonstrate that in response to hydrogen peroxide (H2O2), JAK2 localizes to the nucleus and interacts with MSH2 and MSH6. Inhibition or knockdown of JAK2 reduces the H2O2‐induced chromatin interaction of MSH2, MSH6, DNMT1, and PRC2 members, reduces H2O2‐induced global increase in trimethylation of lysine 27 of histone H3 (H3K27me3), and abrogates oxidative damage‐induced transcriptional repression of candidate TSGs. Moreover, JAK2 mRNA expression is associated with CpG island methylator phenotype (CIMP) status in human colorectal cancer. Our findings provide novel insight into the connection between kinase activation and epigenetic alterations during oxidative damage and inflammation. Environ. Mol. Mutagen. 60:308–319, 2019. © 2018 Wiley Periodicals, Inc.

Elevated levels of reactive oxygen species at sites of chronic inflammation cause oxidative DNA damage in epithelial cells, contributing to carcinogenesis. Aberrant silencing of key genes by promoter CpG island DNA hypermethylation occurs in many cancers that form at sites of chronic inflammation. Yet, it is not completely understood how these aberrant DNA methylation alterations are initiated. We hypothesize that the recruitment of epigenetic silencing proteins to sites of oxidative DNA damage is important for initiating DNA methylation. Here we demonstrate that after hydrogen peroxide (H2O2) treatment, mismatch repair proteins MSH2 and MSH6 become localized to sites of oxidative DNA damage, resulting in the recruitment of DNA methyltransferase 1 (DNMT1) and Polycomb repressive complex 2 (PRC2) members to chromatin. This recruitment results in the formation of repressive chromatin in the promoters of tumor-suppressor genes and the concomitant transient reduction in their expression. We sought to further understand the mechanism that drives H2O2-induced MSH2 and MSH6 chromatin binding. Janus kinase 2 (JAK2) is a kinase that is canonically known to be activated by cytokines and growth hormones and phosphorylate the transcription factor signal transducer and activator of transcription (STATs). Here, we demonstrate that in response to treatment with H2O2, but not interleukin 6 (IL-6), JAK2 translocates to the nucleus and interacts with MSH2 and MSH6. Nuclear JAK2 is important for H2O2-induced chromatin interaction of MSH2, MSH6, DNMT1 and PRC2 members. Interestingly, H2O2-induces a global and site-specific increase in trimethylation of histone H3 at lysine 27 (H3K27me3) that is also dependent on JAK2. Furthermore, by analyzing TCGA datasets, we demonstrate high JAK2 mRNA expression correlates with CpG island methylator phenotype (CIMP) status in gastric and colorectal cancer. All together, these findings suggest JAK2 plays a key role in initiating oxidative damage-induced epigenetic alterations during inflammation-driven tumorigenesis. Ultimately, understanding the mechanism of initiation of cancer-specific promoter DNA hypermethylation may lead to treatment strategies to reduce aberrant epigenetic changes induced by chronic inflammation and therefore reduce tumorigenesis. Citation Format: Ning Ding, Sam Miller, Heather O'Hagan. JAK2 regulates oxidative damage-induced epigenetic alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5317.