Department of Environmental and Molecular Toxicology, North Carolina State University, Campus Box 7633, Raleigh, NC 27695, USA.
FASEB J. 2013 Sep;27(9):3763-74. doi: 10.1096/fj.12-226043. Epub 2013 May 22.
Antioxidant genes such as ferritin are transcriptionally activated in oxidative stress via the antioxidant responsive element (ARE), to which nuclear factor-E2-related factor 2 (Nrf2) binds and activates transcription. Histone modification plays a cooperative and essential role in transcriptional regulation; however, its role in antioxidant gene transcription remains elusive. Arsenic exposure activated ferritin transcription via the ARE concomitant with increased methylation of histones H4Arg3 (H4R3) and H3Arg17 (H3R17). To test our hypothesis that histone H4R3 and H3R17 methylation regulates ferritin transcription, H4R3 and H3R17 protein arginine (R) methyltransferases 1 and 4 (PRMT1 and PRMT4) were investigated. Arsenic exposure of human HaCaT keratinocytes induced nuclear accumulation of PRMT1 and PRMT4, histone H4R3 and H3R17 methylation proximal to the ARE, but not to the non-ARE regions of ferritin genes. PRMT1 or PRMT4 knockdown did not block Nrf2 nuclear accumulation but inhibited Nrf2 binding to the AREs by ∼40% (P<0.05), thus diminishing ferritin transcription in HaCaT and human primary keratinocytes and fibroblasts, causing enhanced cellular susceptibility to arsenic toxicity as evidenced by 2-fold caspase 3 activation. Focused microarray further characterized several oxidative stress response genes are subject to PRMT1 or PRMT4 regulation. Collectively, PRMT1 and PRMT4 regulate the ARE and cellular antioxidant response to arsenic.
抗氧化基因，如铁蛋白，在氧化应激中通过抗氧化反应元件（ARE）被转录激活，核因子-E2 相关因子 2（Nrf2）结合并激活转录。组蛋白修饰在转录调控中发挥协同和必要的作用；然而，其在抗氧化基因转录中的作用仍不清楚。砷暴露通过 ARE 激活铁蛋白转录，同时伴随着组蛋白 H4Arg3（H4R3）和 H3Arg17（H3R17）的甲基化增加。为了验证我们的假设，即组蛋白 H4R3 和 H3R17 甲基化调节铁蛋白转录，研究了组蛋白 H4R3 和 H3R17 蛋白精氨酸（R）甲基转移酶 1 和 4（PRMT1 和 PRMT4）。砷暴露于人 HaCaT 角质形成细胞中诱导 PRMT1 和 PRMT4 的核积累，以及 ARE 附近的组蛋白 H4R3 和 H3R17 甲基化，但不影响铁蛋白基因的非 ARE 区域。PRMT1 或 PRMT4 的敲低并没有阻止 Nrf2 的核积累，但抑制了 Nrf2 与 AREs 的结合约 40%（P<0.05），从而减少了 HaCaT 和人原代角质形成细胞和成纤维细胞中的铁蛋白转录，导致砷毒性的细胞易感性增加，证据是 caspase 3 激活增加了 2 倍。聚焦的微阵列进一步描述了几种氧化应激反应基因受到 PRMT1 或 PRMT4 的调节。总之，PRMT1 和 PRMT4 调节 ARE 和细胞对砷的抗氧化反应。
