Zhang Jianyong, Ohta Tsutomu, Maruyama Atsushi, Hosoya Tomonori, Nishikawa Keizo, Maher Jonathan M, Shibahara Shigeki, Itoh Ken, Yamamoto Masayuki
Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba 305-8577, Japan.
Mol Cell Biol. 2006 Nov;26(21):7942-52. doi: 10.1128/MCB.00700-06. Epub 2006 Aug 21.
NF-E2-related factor 2 (Nrf2) regulates antioxidant-responsive element-mediated induction of cytoprotective genes in response to oxidative stress. The purpose of this study was to determine the role of BRG1, a catalytic subunit of SWI2/SNF2-like chromatin-remodeling complexes, in Nrf2-mediated gene expression. Small interfering RNA knockdown of BRG1 in SW480 cells selectively decreased inducible expression of the heme oxygenase 1 (HO-1) gene after diethylmaleate treatment but did not affect other Nrf2 target genes, such as the gene encoding NADPH:quinone oxidoreductase 1 (NQO1). Chromatin immunoprecipitation analysis revealed that Nrf2 recruits BRG1 to both HO-1 and NQO1 regulatory regions. However, BRG1 knockdown selectively decreased the recruitment of RNA polymerase II to the HO-1 promoter but not to the NQO1 promoter. HO-1, but not other Nrf2-regulated genes, harbors a sequence of TG repeats capable of forming Z-DNA with BRG1 assistance. Similarly, replacement of the TG repeats with an alternative Z-DNA-forming sequence led to BRG1-mediated activation of HO-1. These results thus demonstrate that BRG1, through the facilitation of Z-DNA formation and subsequent recruitment of RNA polymerase II, is critical in Nrf2-mediated inducible expression of HO-1.
核因子E2相关因子2（Nrf2）可调节抗氧化反应元件介导的细胞保护基因的诱导表达，以应对氧化应激。本研究的目的是确定SWI2/SNF2样染色质重塑复合物的催化亚基BRG1在Nrf2介导的基因表达中的作用。用小干扰RNA敲低SW480细胞中的BRG1，可选择性降低马来酸二乙酯处理后血红素加氧酶1（HO-1）基因的诱导表达，但不影响其他Nrf2靶基因，如编码NADPH：醌氧化还原酶1（NQO1）的基因。染色质免疫沉淀分析表明，Nrf2可将BRG1募集至HO-1和NQO1的调控区域。然而，敲低BRG1可选择性降低RNA聚合酶II对HO-1启动子的募集，但不影响其对NQO1启动子的募集。HO-1而非其他Nrf2调控的基因含有一段TG重复序列，该序列在BRG1的协助下能够形成Z-DNA。同样，用另一段能够形成Z-DNA的序列替换TG重复序列可导致BRG1介导的HO-1激活。因此，这些结果表明，BRG1通过促进Z-DNA的形成以及随后募集RNA聚合酶II，在Nrf2介导的HO-1诱导表达中起关键作用。
