Heme oxygenase-1 gene enhancer manifests silencing activity in a chromatin environment prior to oxidative stress
Heme oxygenase-1 gene enhancer manifests silencing activity in a chromatin environment prior to oxidative stress
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DOI：
10.1089/ars.2006.8.60
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发表时间：
2006-01-01
影响因子：
6.6
通讯作者：
Igarashi, K
中科院分区：
文献类型：
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作者：
Dohl, Y;Alam, J;Igarashi, K
血红素加氧酶-1（HO-1）的表达受E1和E2增强子的调控，E1和E2增强子均含有多个Maf识别元件（MARE）。在活细胞中，MARE与Bach 1/MafK异二聚体结合，因此维持HO-1基因（hmox-1）的静止状态：然而，在瞬时转染试验中，它们充当转录增强子。因此，MARE可能仅在染色质环境中显示其功能。通过使用由野生型或突变的E2增强子驱动的EGFP报告基因稳定转染的NIH 3 T3细胞池，我们证明了E2 MARE作为转录沉默子的功能取决于Bach 1/MafK异二聚体在体内仅在染色质环境中的结合。在镉处理后，它们转变为转录增强子。令人惊讶的是，单一的MARE网站并没有表现出这样的fuliction。此外，通过使用DNase I超敏反应测定，我们证明，简单的染色质凝聚不参与Bach 1介导的阻遏。我们的结论是，在染色质环境中，E2 MARE的功能作为转录沉默依赖于BachI/MafK异二聚体的结合。
The expression of heme oxygenase-1 (HO-1) is regulated by El and E2 enhancers, both of which contain multiple Maf recognition elements (MAREs). In living cells, MAREs are bound by Bach1/MafK heterodimers, hence maintaining a quiescent state of the HO-1 gene (hmox-1): However, in transient transfection assays, they act as transcriptional enhancers. Therefore MAREs may manifest their function only in a chromatin environment. By using NIH3T3 cell pools stably transfected with EGFP reporter genes driven by the wild-type or mutated E2 enhancer, we demonstrate that the E2 MAREs function as transcriptional silencers depending on the binding of Bach1/MafK heterodimer in vivo only in a chromatin environment. After cadmium treatment, they switched into transcriptional enhancers. Surprisingly, single MARE site did not exhibit such fuliction. Furthermore, by using DNase I hypersensitivity assay, we demonstrate that simple chromatin condensations were not involved in the Bach1-mediated repression. We conclude that, in a chromatin environment, the E2 MAREs function as transcriptional silencers depending on binding of BachI/MafK heterodimer.