Complex processing patterns of mRNAs of the large ATP synthase operon in Arabidopsis chloroplasts.
Complex processing patterns of mRNAs of the large ATP synthase operon in Arabidopsis chloroplasts.
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DOI：
10.1371/journal.pone.0078265
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Merendino L
中科院分区：
文献类型：
--
作者：
Malik Ghulam M;Courtois F;Lerbs-Mache S;Merendino L
叶绿体是光合细胞器，由蓝藻祖先的内共生进化而来。在叶绿体中，基因仍然像细菌一样组织成转录单位，但相应的多顺反子 mRNA 经历复杂的加工事件，包括基因间切割以及 5' 和 3' 末端定义。当前的处理模型提出，上游顺反子转录本的 3' 端和下游顺反子转录本的 5' 端由相同的 RNA 结合蛋白定义，并且在蛋白质结合位点水平上重叠。我们研究了拟南芥叶绿体中大型 ATP 合酶 (atp) 操纵子的加工机制。该操纵子由质体编码的 RNA 聚合酶从两个启动子开始转录，这两个启动子分别位于操纵子的上游和内部，并包含四个潜在的 RNA 结合蛋白位点。为了研究启动子和蛋白质结合位点对成熟过程的功能意义，我们对 atp 转录物末端进行了详细的作图。我们的数据表明，与玉米相比，具有重叠末端的 atpI 和 atpH 转录本在拟南芥中非常罕见。此外，与 atpF mRNA 重叠的 atpA mRNA 甚至在 3' 端被截短，因此代表降解产物。相反，我们观察到，新生多顺反子 atp 转录物的 5' 末端定义在两个转录起始位点之一之后的第一个蛋白质结合位点，而 3' 末端定义在随后的蛋白质结合位点或前进的 RNA 聚合酶遇到的发夹结构处。我们的结论是，mRNA 保护的重叠机制对于在拟南芥中获得稳定加工的 atp mRNA 的作用有限。我们的研究结果表明，在玉米和拟南芥等不同植物物种的进化过程中，叶绿体进化出了多种策略来产生适合翻译的成熟转录本。
Chloroplasts are photosynthetic cell organelles which have evolved from endosymbiosis of the cyanobacterial ancestor. In chloroplasts, genes are still organized into transcriptional units as in bacteria but the corresponding poly-cistronic mRNAs undergo complex processing events, including inter-genic cleavage and 5′ and 3′ end-definition. The current model for processing proposes that the 3′ end of the upstream cistron transcripts and the 5′ end of the downstream cistron transcripts are defined by the same RNA-binding protein and overlap at the level of the protein-binding site. We have investigated the processing mechanisms that operate within the large ATP synthase (atp) operon, in Arabidopsis thaliana chloroplasts. This operon is transcribed by the plastid-encoded RNA polymerase starting from two promoters, which are upstream and within the operon, respectively, and harbors four potential sites for RNA-binding proteins. In order to study the functional significance of the promoters and the protein-binding sites for the maturation processes, we have performed a detailed mapping of the atp transcript ends. Our data indicate that in contrast to maize, atpI and atpH transcripts with overlapping ends are very rare in Arabidopsis. In addition, atpA mRNAs, which overlap with atpF mRNAs, are even truncated at the 3′ end, thus representing degradation products. We observe, instead, that the 5′ ends of nascent poly-cistronic atp transcripts are defined at the first protein-binding site which follows either one of the two transcription initiation sites, while the 3′ ends are defined at the subsequent protein-binding sites or at hairpin structures that are encountered by the progressing RNA polymerase. We conclude that the overlapping mechanisms of mRNA protection have only a limited role in obtaining stable processed atp mRNAs in Arabidopsis. Our findings suggest that during evolution of different plant species as maize and Arabidopsis, chloroplasts have evolved multiple strategies to produce mature transcripts suitable for translation.
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影响因子：
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作者：
Ghulam, Mustafa Malik;Zghidi-Abouzid, Ouafa;Merendino, Livia
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