Molecular basis distinguishing the DNA binding profile of Nrf2-Maf heterodimer from that of maf homodimer
Molecular basis distinguishing the DNA binding profile of Nrf2-Maf heterodimer from that of maf homodimer
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DOI：
10.1074/jbc.m706863200
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发表时间：
2007-11-16
影响因子：
4.8
通讯作者：
Yamamoto, Masayuki
中科院分区：
文献类型：
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作者：
Kimura, Momoko;Yamamoto, Tae;Yamamoto, Masayuki
Nrf2-small Maf异源二聚体通过抗氧化反应元件激活许多细胞保护基因的转录，是异种生物和氧化应激反应的关键因素。我们的表面等离子体共振-微阵列结合分析显示，Nrf2-MafG异源二聚体和MafG同源二聚体与共识Maf识别元件的结合具有高亲和力，但与共识退化的次优结合序列的结合不同。我们研究了区分Nrf2- MafG异源二聚体与MafG同源二聚体结合谱的分子基础，发现Nrf2基本区的Ala-502残基是其结合特异性的关键决定因素。在Maf蛋白中，酪氨酸位于Nrf2中Ala-502对应的位置。我们制备了一个突变体Nrf2分子，其中Ala- 502被酪氨酸取代。在表面等离子体共振微阵列分析中，Nrf2（A502Y）异源二聚体与MafG的结合特异性与同型二聚体相似。突变体Nrf2(A502Y)-小Maf异源二聚体激活的靶基因与野生型Nrf2-小Maf激活的靶基因有很大的不同，尽管有一些重叠，这表明Nrf2-小Maf异源二聚体调控的靶基因阵列与Maf同源二聚体调控的靶基因阵列在体内有很大的不同。这些结果表明，Nrf2- Maf异源二聚体不同的DNA结合谱对Nrf2作为细胞保护基因的关键调节因子具有重要的生物学意义。我们的论点得到了支持，即Maf同型二聚体和Nrf2-Maf异源二聚体之间的差异DNA结合特异性建立了这些二聚体形成转录因子的差异基因调控。
Nrf2-small Maf heterodimer activates the transcription of many cytoprotective genes through the antioxidant response element and serves as a key factor in xenobiotic and oxidative stress responses. Our surface plasmon resonance-microarray binding analysis revealed that both Nrf2-MafG heterodimer and MafG homodimer bind to the consensus Maf recognition element with high affinity but bind differentially to the suboptimal binding sequences degenerated from the consensus. We examined the molecular basis distinguishing the binding profile of Nrf2- MafG heterodimer from that of MafG homodimer and found that the Ala-502 residue in the basic region of Nrf2 is a critical determinant of its binding specificity. In Maf proteins, a tyrosine resides in the position corresponding to Ala-502 in Nrf2. We prepared a mutant Nrf2 molecule in which Ala- 502 was replaced with tyrosine. In surface plasmon resonance-microarray analysis, heterodimer of Nrf2(A502Y) and MafG displayed a binding specificity similar to that of MafG homodimer. The target genes activated by mutant Nrf2( A502Y)- small Maf heterodimer were largely different, albeit with some overlap, from those activated by wild-type Nrf2-small Maf, indicating that the array of target genes regulated by Nrf2- small Maf heterodimer differs substantially from that regulated by Maf homodimer in vivo. These results suggest that the distinct DNA binding profile of Nrf2- Maf heterodimer is biologically significant for Nrf2 to function as a key regulator of cytoprotective genes. Our contention is supported that the differential DNA binding specificity between Maf homodimers and Nrf2-Maf heterodimers establishes the differential gene regulation by these dimer-forming transcription factors.