SP1-MEDIATED TRANSCRIPTIONAL ACTIVATION IS REPRESSED BY SP3
SP1-MEDIATED TRANSCRIPTIONAL ACTIVATION IS REPRESSED BY SP3
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DOI：
10.1002/j.1460-2075.1994.tb06695.x
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发表时间：
1994-08-15
期刊：
影响因子：
11.4
通讯作者：
SUSKE, G
中科院分区：
文献类型：
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作者：
HAGEN, G;MULLER, S;SUSKE, G
SP1、SP3(SPR-2)和SP4(SPR-1)是人类序列特异的DNA结合蛋白，具有非常相似的结构特征。在本报告中，我们分析了Sp3与Sp1的直接比较。我们已经提出了针对Sp1和Sp3的抗体，并表明像Sp1一样的Sp3蛋白在各种细胞系中都有表达。在不同哺乳动物细胞系中的共转染实验表明，与Sp1和Sp4不同，Sp3不能激活几个Sp1响应启动子。此外，在缺乏内源性Sp因子的果蝇SL2细胞中，SP3也不能激活报告结构。相反，我们发现SP3以线性剂量依赖的方式抑制Sp1介导的激活。缺失DNA结合域的SP3突变体不影响Sp1的激活，这表明这种抑制很可能是由于与Sp1竞争它们的共同结合部位所致。为了确定SP3的任何结构相似的结构域是否能够取代Sp1的部分同源结构域，我们产生了嵌合蛋白并在基因转移实验中测试了它们的激活特性。结果表明，Sp1的富含谷氨酰胺结构域A、B和D结构域都不能被Sp3的同源区域所取代。我们的结果表明，Sp3是Sp家族的抑制性成员。
Sp1, Sp3 (SPR-2) and Sp4 (SPR-1) are human sequence-specific DNA binding proteins with very similar structural features. In this report, we have analyzed Sp3 in direct comparison with Sp1. We have raised antibodies against both Sp1 and Sp3, and show that Sp3 protein, like Sp1 is expressed in various cell lines. Co-transfection experiments in different mammalian cell lines reveal that in contrast to Sp1 and Sp4, Sp3 is not able to activate several Sp1 responsive promoters. In addition, Sp3 also fails to activate reporter constructs in Drosophila SL2 cells lacking endogenous Sp factors. Instead, We find that Sp3 represses Sp1-mediated activation in a linear dose-dependent manner. A mutant of Sp3 lacking the DNA binding domain does not affect activation by Sp1, suggesting that the inhibition is most likely due to the competition with Sp1 for their common binding sites. To determine if any structurally similar domain of Sp3 is able to replace partially homologous domains of Sp1, we have generated chimeric proteins and tested their activation characteristics in gene transfer experiments. It appears that neither the glutamine-rich domains A and B nor the D domain of Sp1 can be replaced by the homologous regions of Sp3. Our results suggest that Sp3 is an inhibitory member of the Sp family.