Molecular Determinants for Small Maf Protein Control of Platelet Production
Molecular Determinants for Small Maf Protein Control of Platelet Production
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DOI：
10.1128/mcb.00798-10
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发表时间：
2011-01-01
影响因子：
5.3
通讯作者：
Yamamoto, Masayuki
中科院分区：
文献类型：
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作者：
Motohashi, Hozumi;Fujita, Rie;Yamamoto, Masayuki
MafG和p45具有碱性区-亮氨酸拉链（bZip）结构域，并形成称为NF-E2的异源二聚体，其是巨核细胞生成的关键调节因子。NF-E2与Maf识别元件（MARE）结合并激活许多血小板基因的转录。由于介导DNA结合和异源二聚化的bZip结构域是为MafG建立的唯一功能结构域，因此假定MafG仅为p45与MARE结合和促进p45介导的转录激活所需。MafG的C-末端区域（其不同于bZip结构域）的分析揭示，该区域含有核基质靶向信号。我们使用转基因互补拯救试验来描述MafG C末端在体内的功能。将表达缺少C末端的突变MafG蛋白（MafGΔC）的转基因小鼠与aMafG-null背景杂交。复合突变小鼠表现出严重的血小板减少症和脾肿大，这与p45基因敲除小鼠的表型相似。MafG C末端对于前血小板形成和血小板基因活化是必需的，但对于p45与MARE的结合不是必需的。这些结果表明，MafG C末端是NF-E2功能所必需的，并表明NF-E2有效靶向特定的核支架对于实现高水平活性是重要的。
MafG and p45 possess basic region-leucine zipper (bZip) domains and form a heterodimer called NF-E2, a key regulator of megakaryopoiesis. NF-E2 binds to the Maf recognition element (MARE) and activates transcription of many platelet genes. Since the bZip domain, which mediates DNA binding and heterodimerization, is the only functional domain established for MafG, it has been assumed that MafG is required only for p45 binding to MARE and to facilitate p45-mediated transcriptional activation. Analysis of the C-terminal region of MafG, which is distinct from the bZip domain, revealed that this region contains a nuclear matrix-targeting signal. We used a transgenic complementation rescue assay to delineate the function of the MafG C terminusin vivo. Transgenic mice expressing a mutant MafG protein lacking the C terminus (MafGΔC) were crossed into aMafG-null background. The compound mutant mice displayed severe thrombocytopenia and splenomegaly, which phenocopiedp45-null mice. The MafG C terminus is essential for proplatelet formation and platelet gene activation but not for p45 binding to MARE. These results demonstrate that the MafG C terminus is required for NF-E2 function and suggest that efficient targeting of NF-E2 to a specific nuclear scaffold is important to achieve high-level activity.