Cryptic promoter activation occurs by at least two different mechanisms in the Arabidopsis genome
Cryptic promoter activation occurs by at least two different mechanisms in the Arabidopsis genome
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DOI：
10.1111/tpj.15420
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发表时间：
2021-08-02
期刊：
影响因子：
7.2
通讯作者：
Obokata, Junichi
中科院分区：
文献类型：
--
作者：
Kudo, Hisayuki;Matsuo, Mitsuhiro;Obokata, Junichi
在植物基因组的基因陷阱筛选中，无启动子的报告构建体通常在不捕获注释的基因启动子的情况下表达。这种现象的分子基础，这已被解释为隐蔽启动子的陷阱，是知之甚少。在此，我们发现隐蔽启动子激活通过至少两种不同的机制发生，使用拟南芥基因诱捕系，其中没有明显启动子序列的萤火虫荧光素酶（LUC）开放阅读框（ORF）从基因间区域表达：一种机制是“隐蔽启动子捕获”，其中LUC ORF捕获预先存在的由H3 K4 me 3和H2A.Z标记的启动子样染色质，另一种是“启动子从头起源”，即在插入的LUC ORF的5 '端附近新形成启动子染色质。后一个发现提出了一个问题，即插入的LUC ORF序列如何参与这种现象。为了验证这一点，我们在转基因植物中进行了嵌合LUC基因的模型实验。使用拟南芥psaH 1启动子-LUC构建体，我们发现，转录起始位点（TSS）发生的功能性核心启动子区域，不能简单地由上游或核心启动子序列决定;相反，它的位置接近插入的LUC ORF序列更关键。该结果表明，编码序列的插入改变了植物基因组中TSS的局部分布。讨论了这两种潜在启动子激活机制对植物基因组进化和内共生基因转移的可能影响。
In gene-trap screening of plant genomes, promoterless reporter constructs are often expressed without trapping of annotated gene promoters. The molecular basis of this phenomenon, which has been interpreted as the trapping of cryptic promoters, is poorly understood. Here, we found that cryptic promoter activation occurs by at least two different mechanisms using Arabidopsis gene-trap lines in which a firefly luciferase (LUC) open reading frame (ORF) without an apparent promoter sequence was expressed from intergenic regions: one mechanism is 'cryptic promoter capturing', in which the LUC ORF captured pre-existing promoter-like chromatin marked by H3K4me3 and H2A.Z, and the other is 'promoter de novo origination', in which the promoter chromatin was newly formed near the 5 ' end of the inserted LUC ORF. The latter finding raises a question as to how the inserted LUC ORF sequence is involved in this phenomenon. To examine this, we performed a model experiment with chimeric LUC genes in transgenic plants. Using Arabidopsis psaH1 promoter-LUC constructs, we found that the functional core promoter region, where transcription start sites (TSSs) occur, cannot simply be determined by the upstream nor core promoter sequences; rather, its positioning proximal to the inserted LUC ORF sequence was more critical. This result suggests that the insertion of the coding sequence alters the local distribution of TSSs in the plant genome. The possible impact of the two types of cryptic promoter activation mechanisms on plant genome evolution and endosymbiotic gene transfer is discussed.