The mechanism of heme oxygenase-1 (HO-1) induction by heat shock (HS) loading remains unclear. Here, we investigated the contribution of transcription factors to HS-induced HO-1 expression, using a rat hepatoma cell line (H-4-II-E). Our results demonstrated that HS treatment resulted in a marked induction of HO-1. Immunohistochemical analysis showed a slight mismatch in the expression levels of HO-1 and HSP70 by HS among cells, suggesting a conflict between multiple induction mechanisms. We observed HS-induced nuclear localization of, not only phosphorylated HSF1 but also NRF2, which is a typical transcription factor activated by oxidative stress. HSF1 knockdown in H-4-II-E markedly reduced HO-1 induction by HS, while NRF2 knockdown resulted in a partial effect. The chromatin immunoprecipitation assay demonstrated that HS loading resulted in significant binding of HSF1 to the HSE in the promoter proximal region of HO-1 gene and another HSE located close to the Maf recognition element (MARE) in the −4 kb upstream enhancer region 1, where NRF2 also bound, together with basic leucine zipper transcription factor 1, a negative transcription factor of HO-1. These observations indicate that HO-1 induction by HS is mainly mediated by HSF1 binding to the proximal HSE. NRF2 binding to MARE by HS is predominantly suppressed by an increased binding of BACH1.

中文翻译：

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热休克对大鼠肝癌细胞系血红素加氧酶 1 的诱导受 HSF1、NRF2 和 BACH1 协调功能的调节

热休克 (HS) 负载诱导血红素加氧酶-1 (HO-1) 的机制仍不清楚。在这里，我们使用大鼠肝癌细胞系 (H-4-II-E) 研究了转录因子对 HS 诱导的 HO-1 表达的贡献。我们的结果表明，HS 处理导致 HO-1 的显着诱导。免疫组织化学分析显示细胞间 HS 对 HO-1 和 HSP70 的表达水平略有不匹配，表明多种诱导机制之间存在冲突。我们观察到 HS 诱导的磷酸化 HSF1 和 NRF2 的核定位，NRF2 是由氧化应激激活的典型转录因子。H-4-II-E 中的 HSF1 敲低显着降低了 HS 对 HO-1 的诱导，而 NRF2 敲低导致部分效应。染色质免疫沉淀测定表明，HS 加载导致 HSF1 与 HO-1 基因启动子近端区域中的 HSE 显着结合，另一个 HSE 位于 -4 kb 上游增强子区域 1 中靠近 Maf 识别元件 (MARE) 的位置，其中 NRF2 还与碱性亮氨酸拉链转录因子 1 结合，这是一种 HO-1 的负转录因子。这些观察结果表明，HS 对 HO-1 的诱导主要由 HSF1 与近端 HSE 结合介导。HS 与 MARE 的 NRF2 结合主要受到 BACH1 结合增加的抑制。连同碱性亮氨酸拉链转录因子 1，HO-1 的负转录因子。这些观察结果表明，HS 对 HO-1 的诱导主要由 HSF1 与近端 HSE 结合介导。HS 与 MARE 的 NRF2 结合主要受到 BACH1 结合增加的抑制。连同碱性亮氨酸拉链转录因子 1，HO-1 的负转录因子。这些观察结果表明，HS 对 HO-1 的诱导主要由 HSF1 与近端 HSE 结合介导。HS 与 MARE 的 NRF2 结合主要受到 BACH1 结合增加的抑制。