Breen G A, Jordan E M
Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson 75083-0688, USA.
Gene Expr. 1998;7(3):163-70.
The F1F0 ATP synthase is the central enzyme complex of the mitochondrial oxidative phosphorylation system synthesizing ATP from ADP and Pi. Our laboratory has been studying the transcriptional regulation of the nuclear gene that encodes the alpha-subunit of the mammalian mitochondrial ATP synthase complex (ATPA). We have previously identified an initiator element in the core promoter that plays an important role in expression of this gene. In this article, we demonstrate that ectopic expression of the transcription factor, upstream stimulatory factor 2 (USF2), transactivates the ATPA gene through this initiator element. Importantly, cotransfection of a dominant-negative USF2 mutant significantly reduces both the basal activity and the level of activation of the ATPA initiator by coexpressed USF2 demonstrating the role of endogenous USF2 proteins in this activation. We also identify several nucleotides in the ATPA initiator element that are important for both basal activity and USF2-dependent transactivation. We have also previously determined that the binding of the multifunctional regulatory protein, YY1, to this initiator element can positively regulate the ATPA gene. Here, we show that expression of YY1 together with USF2 results in a decreased level of activation of the ATPA initiator relative to expression of USF2 alone, suggesting competition between these two regulatory proteins.
F1F0 ATP合酶是线粒体氧化磷酸化系统的核心酶复合物，可利用二磷酸腺苷（ADP）和无机磷酸（Pi）合成三磷酸腺苷（ATP）。我们实验室一直在研究编码哺乳动物线粒体ATP合酶复合物α亚基（ATPA）的核基因的转录调控。我们之前在核心启动子中鉴定出一个起始元件，该元件在该基因的表达中起重要作用。在本文中，我们证明转录因子上游刺激因子2（USF2）的异位表达通过该起始元件反式激活ATPA基因。重要的是，共转染显性负性USF2突变体可显著降低基础活性以及共表达的USF2对ATPA起始子的激活水平，这证明了内源性USF2蛋白在这种激活中的作用。我们还在ATPA起始元件中鉴定出几个对基础活性和USF2依赖性反式激活都很重要的核苷酸。我们之前还确定多功能调节蛋白YY1与该起始元件的结合可正向调节ATPA基因。在这里，我们表明与单独表达USF2相比，YY1与USF2共同表达导致ATPA起始子的激活水平降低，这表明这两种调节蛋白之间存在竞争。
