Regulation of the human MAT2A gene encoding the catalytic α2 subunit of methionine adenosyltransferase, MAT II -: Gene organization, promoter characterization, and identification of a site in the proximal promoter that is essential for its activity
Regulation of the human MAT2A gene encoding the catalytic α2 subunit of methionine adenosyltransferase, MAT II -: Gene organization, promoter characterization, and identification of a site in the proximal promoter that is essential for its activity
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DOI：
10.1074/jbc.m002347200
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发表时间：
2001-03-30
影响因子：
4.8
通讯作者：
Kotb, M
中科院分区：
文献类型：
--
作者：
Halim, AB;LeGros, L;Kotb, M
哺乳动物蛋氨酸腺苷转移酶II （MAT II）由一个催化α 2/ α 2 '和一个调节β亚基组成。α 2亚基表达的上调与细胞内s -腺苷甲硫氨酸水平的增加有关，s -腺苷甲硫氨酸是主要的甲基供体，也是细胞代谢和多胺合成的关键化合物。先前的研究表明，在正常细胞和恶性细胞中，alpha2亚基的表达受到差异调控。为了描述alpha2亚基表达差异调控的分子基础，我们克隆并表征了人类MAT2A基因及其启动子，并定义了包含增强子和抑制子元件的区域。对MAT2A基因近端启动子的详细功能表征表明，含有3个Spl位点的探针（Spl- 1位于-14位点，Sp1-2位于-47位点，Sp1-3位于-69位点）可形成3个主要的蛋白质- dna复合物，与仅含有Sp1-3位点的-76和-54之间的探针复制序列竞争，或该位点发生突变，可消除复合物的形成。此外，Sp1-3位点的突变，而非Spl- 1或Sp1-2位点的突变，对体内启动子活性的抑制率约为85%。Supershift实验表明，转录因子Sp2和Sp3是Sp1-3位点形成的复合物的一部分，Spl似乎没有直接参与。数据表明，复合物的形成始于Sp1-3位点，这似乎是启动子活性所必需的。然而，近端启动子的其他区域也可能参与MAT2A基因表达的调控。这些研究可能有助于揭示正常和白血病T细胞中MAT2A表达差异调控的分子基础。
Mammalian methionine adenosyltransferase II (MAT II) consists of a catalytic alpha2/alpha2 ' and a regulatory beta subunit. Up-regulation of alpha2 subunit expression is associated with increased intracellular levels of S-adenosylmethionine, the major methyl group donor and a key compound in cell metabolism and polyamine synthesis. Previous studies have shown that expression of the alpha2 subunit is differentially regulated in normal and malignant cells, To delineate the molecular basis for the differential regulation of alpha2 subunit expression, we cloned and characterized the human MAT2A gene and its promoter and defined regions that contain enhancer and repressor elements, Detailed functional characterization of the proximal promoter of the MAT2A gene revealed the formation of three major protein-DNA complexes with probes containing three Spl sites (Spl-l at -14, Sp1-2 at -47, and Sp1-3 at -69), Competition with a probe copying sequence between -76 and -54, which contains the Sp1-3 site only, or mutation of this site, abolished complex formation. Furthermore, mutation of the Sp1-3 site, but not the Spl-l or Sp1-2 sites, inhibited the in vivo promoter activity by similar to 85%, Supershift assays showed that the transcription factors Sp2 and Sp3 are part of the complexes formed at the Sp1-3 site, and that Spl does not appear to be directly involved. The data indicate that complex formation is initiated at site Sp1-3, which appears to be essential for promoter activity. However, other regions of the proximal promoter may also contribute to the regulation of MAT2A gene expression. These studies may lead to the delineation of the molecular basis for the differential regulation of MAT2A expression in normal and leukemic T cells.