Modulation of the murine peroxisome proliferator-activated receptor gamma 2 promoter activity by CCAAT/enhancer-binding proteins.
Modulation of the murine peroxisome proliferator-activated receptor gamma 2 promoter activity by CCAAT/enhancer-binding proteins.
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DOI：
10.1074/jbc.m003593200
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发表时间：
2000-09
期刊：
影响因子：
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通讯作者：
G. Elberg;J. Gimble;S. Tsai
中科院分区：
文献类型：
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作者：
G. Elberg;J. Gimble;S. Tsai
过氧化物酶体增殖激活受体γ (PPARgamma)和CCAAT/增强子结合蛋白（C/ ebp）是脂肪细胞分化和功能所必需的转录调节因子。先前的研究结果表明，PPARgamma2的转录受C/EBP家族成员的调控。我们在这里证明，C/ ebppalpha和C/EBPdelta，而不是C/EBPbeta，在瞬时转染的3T3-L1前脂肪细胞中诱导PPARgamma2启动子的活性，并结合两个并置于低亲和力的C/EBP结合位点。嵌合体含有互换的C/EBPbeta -C/EBPbeta n端反激活域和C端DNA结合二聚化域，结果表明C/EBPbeta的n端部分阻止其与PPARgamma2启动子结合。事实上，缺乏分子n端部分的C/EBPbeta缺失突变体能够与PPARgamma2启动子结合。我们进一步证明，DNA结合域上游的氨基酸184-212之间的一个区域的缺失，允许C/EBPbeta与PPARgamma2启动子结合，暗示C/EBPbeta中有一个抑制区域调节DNA与PPARgamma2启动子的结合特异性。综上所述，本研究表明C/EBPbeta不能结合小鼠PPARgamma2启动子中的C/EBP结合位点，而C/EBPalpha或C/EBPdelta则不能。缺乏结合是由于C/EBPbeta DNA结合域的n端区域。我们的发现阐明了C/EBP异构体差异调节PPARgamma2启动子转激活的机制。
Peroxisome proliferator-activated receptor gamma (PPARgamma) and CCAAT/enhancer-binding proteins (C/EBPs) are transcriptional regulators essential for adipocyte differentiation and function. Previous findings indicate that PPARgamma2 transcription is regulated by members of the C/EBP family. We demonstrate here that C/EBPalpha and C/EBPdelta, but not C/EBPbeta, induce the activity of the PPARgamma2 promoter in transiently transfected 3T3-L1 preadipocytes and bind to two juxtaposed low affinity C/EBP binding sites. Results obtained with chimeras containing interchanged C/EBPalpha-C/EBPbeta N-terminal transactivation domain and C-terminal DNA binding dimerization domain indicate that the N-terminal part of C/EBPbeta prevents it from binding to the PPARgamma2 promoter. Indeed, deletion mutants of C/EBPbeta lacking the N-terminal part of the molecule are able to bind to the PPARgamma2 promoter. We further demonstrate that deletion of a region located between amino acids 184-212, upstream of the DNA binding domain, permits C/EBPbeta binding to the PPARgamma2 promoter, implicating an inhibitory region in C/EBPbeta for modulating DNA binding specificity to the PPARgamma2 promoter. In summary, this study indicates that C/EBPbeta but not C/EBPalpha or C/EBPdelta is unable to bind to C/EBP binding sites in the mouse PPARgamma2 promoter. The lack of binding is due to a region N-terminal of the C/EBPbeta DNA binding domain. Our findings illustrate a mechanism by which C/EBP isoforms differentially modulate the transactivation of the PPARgamma2 promoter.