Nrf2, a Cap'n'Collar transcription factor, regulates induction of the heme oxygenase-1 gene
Nrf2, a Cap'n'Collar transcription factor, regulates induction of the heme oxygenase-1 gene
复制标题
DOI：
10.1074/jbc.274.37.26071
复制
发表时间：
1999-09-10
影响因子：
4.8
通讯作者：
Cook, JL
中科院分区：
文献类型：
--
作者：
Alam, J;Stewart, D;Cook, JL
应激反应元件通过多种试剂介导小鼠血红素加氧酶-1 (HO-1) 基因的诱导，类似于激活蛋白-1 (Jun/Fos)、Maf 和 Cap'n'Collar/碱性亮氨酸拉链 (CNC-bZIP) 家族蛋白的结合位点。在 L929 成纤维细胞中，仅在 CNC-bZIP 类蛋白质中观察到 HO-1 增强子-报告基因融合基因的显着激活，其中 Nrf2 表现出最高水平的反式激活，在 25 至 30 倍之间。为了进一步研究该因子在 HO-1 基因调控中的作用，产生了显性失活突变体 Nrf2M，并在 L929 细胞中条件表达。在细胞质和核部分中检测到突变蛋白，但不影响细胞生长。在Nrf2M过表达的条件下，响应血红素、镉、锌、亚砷酸盐和叔丁基氢醌的HO-1 mRNA积累被抑制85-95%。相比之下，c-Jun 显性失活突变体的过度表达会降低 L929 细胞的生长，但不会抑制 HO-1 基因的激活。 Nrf2 不形成同二聚体，但 CNC-bZIP 小 Maf 蛋白异二聚体和 Nrf2 Jun 蛋白复合物被认为可充当反式激活剂。然而，Jun 蛋白或 p18 的共表达没有显着影响或抑制 Nrf2 介导的反式激活。总而言之，这些结果表明 Nrf2 参与了 HO-1 基因的诱导，但表明该功能中的 Nrf2 伴侣是 p18 或 Jun 蛋白之外的一个因子。
Stress response elements, which mediate induction of the mouse heme oxygenase-l (HO-1) gene by several agents, resemble the binding site for the activator protein-1 (Jun/Fos), Maf, and Cap'n'Collar/basic leucine zipper (CNC-bZIP) families of proteins. In L929 fibroblasts, significant activation of an HO-1 enhancer-reporter fusion gene was observed only with the CNC-bZIP class of proteins with Nrf2 exhibiting the highest level of transactivation, between 25- and 30-fold. To further examine the role of this factor in HO-1 gene regulation, a dominant-negative mutant, Nrf2M, was generated and conditionally expressed in L929 cells. The mutant protein was detected in cytoplasmic and nuclear fractions but did not affect cell growth. Under conditions of Nrf2M overexpression, HO-1 mRNA accumulation in response to heme, cadmium, zinc, arsenite, and tert-butylhydroquinone was inhibited by 85-95%. In contrast, overexpression of a dominant-negative mutant of c-Jun decreased L929 cell growth but did not inhibit HO-1 gene activation. Nrf2 does not homodimerize, but CNC-bZIP small Maf protein heterodimers and Nrf2 Jun protein complexes are proposed to function as trans-activators. Coexpression of Jun proteins or p18, however, had no significant affect or inhibited Nrf2-mediated trans-activation. Taken together, these results implicate Nrf2 in the induction of the HO-1 gene but suggest that the Nrf2 partner in this function is a factor other than p18 or Jun proteins.