Alam Jawed, Killeen Erin, Gong Pengfei, Naquin Ryan, Hu Bin, Stewart Daniel, Ingelfinger Julie R, Nath Karl A
Department of Molecular Genetics, Ochsner Clinic Foundation, New Orleans 70121, USA.
Am J Physiol Renal Physiol. 2003 Apr;284(4):F743-52. doi: 10.1152/ajprenal.00376.2002. Epub 2002 Nov 26.
The mechanism of heme oxygenase-1 gene (ho-1) activation by heme in immortalized rat proximal tubular epithelial cells was examined. Analysis of the ho-1 promoter identified the heme-responsive sequences as the stress-response element (StRE), multiple copies of which are present in two enhancer regions, E1 and E2. Electrophoretic mobility shift assays identified Nrf2, MafG, ATF3, and Jun and Fos family members as StRE-binding proteins; binding of Nrf2, MafG, and ATF3 was increased in response to heme. Dominant-negative mutants of Nrf2 and Maf, but not of c-Fos and c-Jun, inhibited basal and heme-induced expression of an E1-controlled luciferase gene. Heme did not affect the transcription activity of Nrf2, dimerization between Nrf2 and MafG, or the level of MafG, but did stimulate expression of Nrf2. Heme did not influence the level of Nrf2 mRNA but increased the half-life of Nrf2 protein from approximately 10 min to nearly 110 min. These results indicate that heme promotes stabilization of Nrf2, leading to accumulation of Nrf2. MafG dimers that bind to StREs to activate the ho-1 gene.
研究了血红素在永生化大鼠近端肾小管上皮细胞中激活血红素加氧酶-1基因（ho-1）的机制。对ho-1启动子的分析确定血红素反应序列为应激反应元件（StRE），其多个拷贝存在于两个增强子区域E1和E2中。电泳迁移率变动分析确定Nrf2、MafG、ATF3以及Jun和Fos家族成员为StRE结合蛋白；血红素刺激后，Nrf2、MafG和ATF3的结合增加。Nrf2和Maf的显性负性突变体可抑制E1控制的荧光素酶基因的基础表达和血红素诱导的表达，但c-Fos和c-Jun的显性负性突变体则无此作用。血红素不影响Nrf2的转录活性、Nrf2与MafG之间的二聚化或MafG的水平，但可刺激Nrf2的表达。血红素不影响Nrf2 mRNA的水平，但可将Nrf2蛋白的半衰期从约10分钟延长至近110分钟。这些结果表明，血红素促进Nrf2的稳定，导致Nrf2积累。与StRE结合以激活ho-1基因的MafG二聚体。
