S phase and weristem-specific expression of the tobacco RNR1b gene is mediated by an E2F element located in the 5′ leader sequence
S phase and weristem-specific expression of the tobacco RNR1b gene is mediated by an E2F element located in the 5′ leader sequence
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DOI：
10.1074/jbc.m200959200
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发表时间：
2002-05-17
影响因子：
4.8
通讯作者：
Philipps, G
中科院分区：
文献类型：
--
作者：
Chabouté, ME;Clément, B;Philipps, G
RB/E2F通路参与控制真核细胞周期的G(1)/S转变，其中各种S期基因被特定的E2F因子激活。核糖核苷酸还原酶（rna - r）在DNA合成途径中起着重要作用。早期的研究表明，烟草中至少有两个RNR1基因（RNR1a和RNR1b）和一个RNR2基因。在烟草同步BY2细胞中，RNR1b基因的表达在S期达到最高水平。为了研究RNR1b基因的转录调控，对其启动子区域进行了克隆和测序。与动物不同，烟草RNR1b启动子含有一个一致的e2f结合位点。令人惊讶的是，这个位点是在基因的先导序列中发现的。我们在这里通过凝胶位移分析和抗体竞争表明，一个核复合物特异性地结合了这个基序，而E2F因子是这个复合物的一部分。利用报告基因分析，检测了烟草同步细胞S期和植物分生组织中RNR1b启动子的活性。E2F元素的突变大大降低了这两种活性。烟草RNR1b基因在分生组织和S期特异性表达中，首次在植物中发现单个E2F基序，该基序在烟草RNR1b基因的分生组织和S期特异性表达中起重要作用。
The RB/E2F pathway is involved in the control of the G(1)/S transition of the eukaryotic cell cycle where various S phase genes are activated by specific E2F factors. Ribonucleotide reductase (RN-R) plays an essential role in the DNA synthesis pathway. Earlier studies showed that there are at least two RNR1 genes (RNR1a and RNR1b) and one RNR2 gene in tobacco. In synchronized tobacco BY2 cells, RNR1b gene expression is at its highest level in S phase. To investigate transcriptional regulation of the RNR1b gene, its promoter region was cloned and sequenced. Unlike its animal counterparts, the tobacco RNR1b promoter contains a consensus E2F-binding site. Surprisingly, this site is found in the leader sequence of the gene. We show here by gel shift analysis and antibody competition that one nuclear complex specifically binds this motif, and an E2F factor is part of this complex. Using reporter gene analysis, tobacco RNR1b promoter activity was detected during S phase in synchronized cells and in plant meristematic tissues. Mutation of the E2F element substantially reduced both activities. For the first time in plants, a single E2F motif found in the leader sequence plays an important role in the meristem and S phase-specific expression of the tobacco RNR1b gene.