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Organization and regulatory mechanism of the promoters unique to photosynthesis nuclear genes

光合作用核基因特有启动子的组织与调控机制

基本信息

批准号：
14340253
负责人：
OBOKATA Junichi
金额：
$ 9.34万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Core promoter is a region where preinitiation complex containing RNA polymerase II assembles, and located around the transcription start sites. In plant nuclear genes, core promoters generally contain TATA boxes as an essential element, and are believed to be indispensable for basal transcription but not involved in gene-specific regulation. However, we recently found the case where above assumption is not correct. The core promoter of a tobacco photosystem I gene, psaDb contains a pyrimidine-rich initiator element (Inr) but not a TATA box ; this core promoter architecture is referred to as a TATA-/Inr+ type. Experiments with various chimeric promoters revealed that the light-responsive transcription of psaDb effectively occurs only when the core promoter contains Inr, and TATA box cannot compensate for this Inr. This is the first example in plant genes that the core promoter architecture plays a pivotal role in gene-specific regulation. This finding raised a next question if this selective activation of the core promoter by upstream regulatory elements is unique to psaDb or common to a certain group of plant genes. In this study, we systematically analyzed the core promoter architecture of plant nuclear genes, and demonstrate that PSI genes constitute a unique group in respect to the architecture and function of their core promoters. The core promoters of the PSI gene group are generally TATA-/Inr+ or TATA-/Inr-types, and especially in the latter case, we found no promoter consensus motif so far identified in eukaryotic promoter systems. Swapping experiments of the upstream and core promoters between PSI genes and other TATA-containing plant genes revealed that core promoter requirement of PSI genes is quite different from that of the majority of plant nuclear genes.

核心启动子是含有RNA聚合酶II的起始前复合物组装的区域，位于转录起始位点周围。在植物核基因中，核心启动子一般包含TATA box作为必需元件，被认为是基础转录所必需的，但不参与基因特异性调控。然而，我们最近发现了上述假设不正确的情况。烟草光系统I基因的核心启动子psaDb含有一个富含嘧啶的引发元素（Inr），但不含TATA盒；这个核心启动子架构被称为TATA-/Inr+型。对各种嵌合启动子的实验表明，psaDb的光响应转录只有在核心启动子含有Inr时才能有效发生，而TATA box不能补偿这种Inr。这是植物基因中首次发现核心启动子结构在基因特异性调控中起关键作用。这一发现提出了下一个问题，上游调控元件对核心启动子的选择性激活是psaDb独有的还是某一组植物基因共有的？本研究系统分析了植物核基因的核心启动子结构，证明了PSI基因在其核心启动子的结构和功能上是一个独特的群体。PSI基因群的核心启动子通常为TATA-/Inr+或TATA-/Inr型，特别是在后一种情况下，我们迄今未在真核启动子系统中发现启动子共识基序。PSI基因的上游启动子和核心启动子与其他含tata的植物基因的交换实验表明，PSI基因对核心启动子的需求与大多数植物核基因有很大的不同。