BINDING-SITE REQUIREMENTS AND DIFFERENTIAL REPRESENTATION OF TGA FACTORS IN NUCLEAR ASF-1 ACTIVITY
BINDING-SITE REQUIREMENTS AND DIFFERENTIAL REPRESENTATION OF TGA FACTORS IN NUCLEAR ASF-1 ACTIVITY
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DOI：
10.1093/nar/23.18.3778
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发表时间：
1995-09-25
影响因子：
14.9
通讯作者：
LAM, YKP
中科院分区：
文献类型：
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作者：
LAM, E;LAM, YKP
激活序列因子1（ASF-1）是一种存在于单子叶植物和双子叶植物中的具有核DNA结合活性的因子，它与病毒和T-DNA基因中的几个含TGACG的元件相互作用，其原型是CaMV 35 S启动子的as-1元件和章鱼碱合成酶启动子的ocs元件，这类顺式作用元件可以响应生长素和水杨酸处理，与这些观察结果一致，我们已经表明ASF-1可以与生长素诱导的烟草基因GNT 35的启动子元件相互作用，GNT 35编码谷胱甘肽S-转移酶。表征在体内构成ASF-1活性的核因子将是理解这种诱导现象的重要一步，碱性亮氨酸拉链（bZIP）蛋白的TGA家族是ASF-1核因子的良好候选者，然而，在拟南芥中可能有多达七个不同的TGA基因，其中五个现已被报道，在本研究中，我们在体外表达了编码这五种拟南芥TGA因子中的四种的cDNA，并使用两种比较了它们的DNA结合行为。我们还利用针对拟南芥已知的5种伊加因子中的3种制备的特异性抗血清，研究了这3种蛋白质在根和叶核提取物中ASF-1活性的相对丰度。我们的结果表明，这些TGA因子与DNA的结合具有不同程度的协同性，它们与AS-1的相对亲和力也可能存在显著差异，超位移分析的结果表明，只有一个TGA因子代表了核ASF-1活性的重要组成部分，拟南芥TGA 2包含类似的33%和50%的ASF-1活性分别在根和叶核提取物中检测到。这些结果表明，TGA因子家族的每个成员可能受到差异调节，并且它们可能凭借其独特的DNA结合特性发挥不同的作用。此外，由于这些因子中的每一个的转录本可以在各种植物组织中检测到，因此转录后调节可能在确定它们对给定细胞类型中的核ASF-1的贡献中起重要作用。
Activating sequence factor 1 (ASF-1) is a nuclear DNA-binding activity that is found in monocots and dicots, It interacts with several TGACG-containing elements that have been characterized from viral and T-DNA genes, the prototypes of which are the as-1 element of the CaMV 35S promoter and the ocs element from the octopine synthase promoter, This class of cis-acting elements can respond to auxin and salicylic acid treatments, Consistent with these observations, we have shown that ASF-1 can interact with promoter elements of an auxin-inducible tobacco gene GNT35, encoding a glutathione S-transferase. Characterization of the nuclear factors that make up ASF-1 activity in vivo will be an important step toward understanding this induction phenomenon, The TGA family of basic-leucine-zipper (bZIP) proteins are good candidates for the ASF-1 nuclear factor, However, there may be as many as seven distinct TGA genes in Arabidopsis, five of which have now been reported, In this study, we expressed the cDNAs that encode four of these five Arabidopsis TGA factors in vitro and compared their DNA-binding behavior using two. types of TGACG-containing elements, With specific antisera prepared against three of the five known Arabidopsis IGA factors, we also investigated the relative abundance of these three proteins within the ASF-1 activities of root and leaf nuclear extracts, Our results indicate that these TGA factors bind to DNA with different degrees of cooperativity and their relative affinity toward as-1 also can differ significantly, The results of a supershift assay suggested that only one of the three TGA factors represented a significant component of nuclear ASF-1 activity, Arabidopsis TGA2 comprises similar to 33 and 50% of the ASF-1 activity detected in root and leaf nuclear extracts respectively. These results suggest that each member of the TGA factor family may be differentially regulated and that they may play different roles by virtue of their distinct DNA-binding characteristics. Furthermore, since transcripts for each of these factors can be detected in various plant tissues, post-transcriptional regulation may play an important part in determining their contribution to nuclear ASF-1 in a given cell type.