Arabidopsis IWS1 interacts with transcription factor BES1 and is involved in plant steroid hormone brassinosteroid regulated gene expression
Arabidopsis IWS1 interacts with transcription factor BES1 and is involved in plant steroid hormone brassinosteroid regulated gene expression
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DOI：
10.1073/pnas.0909198107
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发表时间：
2010-02-23
影响因子：
11.1
通讯作者：
Yin, Yanhai
中科院分区：
文献类型：
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作者：
Li, Lei;Ye, Huaxun;Yin, Yanhai
油菜素类固醇激素（brassinosteroids，BRs）是植物生长发育的重要调节因子。BRs通过膜定位受体BRI 1和其他几种信号传导组分来调节BES 1和BZR 1家族转录因子，进而控制数百个靶基因的表达。然而，关于BES 1/BZR 1调节基因表达的转录机制的知识是有限的。通过正向遗传学方法，我们已经发现，拟南芥的相互作用与Spt 6（AtIWS 1），一个进化上保守的蛋白质参与RNA聚合酶II（RNAPII）后募集和转录延伸过程，是BR诱导的基因表达所必需的。AtIWS 1的功能缺失突变导致拟南芥的整体侏儒症、BR反应降低、BR诱导的基因表达的全基因组降低以及对转录延伸抑制剂的超敏反应。此外，AtIWS 1在体外和体内都与BES 1相互作用。染色质免疫沉淀实验表明，AtIWS 1的存在下，丰富的转录以及启动子区的目标基因在BR诱导的条件下。我们的研究结果表明，AtIWS 1招募到靶基因的BES 1，以促进基因表达在转录延伸过程中。最近的基因组研究表明，大量的基因可以在RNAPII募集后的步骤进行调节，然而，这种调节的机制还没有很好地建立。因此，这项研究不仅确立了AtIWS 1在植物类固醇诱导的基因表达中的重要作用，而且还表明了一种令人兴奋的可能性，即IWS 1蛋白可以作为途径特异性激活剂的靶标，从而为控制基因表达提供了一种独特的机制。
Plant steroid hormones, brassinosteroids (BRs), regulate essential growth and developmental processes. BRs signal through membrane-localized receptor BRI1 and several other signaling components to regulate the BES1 and BZR1 family transcription factors, which in turn control the expression of hundreds of target genes. However, knowledge about the transcriptional mechanisms by which BES1/BZR1 regulate gene expression is limited. By a forward genetic approach, we have discovered that Arabidopsis thaliana Interact-With-Spt6 (AtIWS1), an evolutionarily conserved protein implicated in RNA polymerase II (RNAPII) postrecruitment and transcriptional elongation processes, is required for BR-induced gene expression. Loss-of-function mutations in AtIWS1 lead to overall dwarfism in Arabidopsis, reduced BR response, genome-wide decrease in BR-induced gene expression, and hypersensitivity to a transcription elongation inhibitor. Moreover, AtIWS1 interacts with BES1 both in vitro and in vivo. Chromatin immunoprecipitation experiments demonstrated that the presence of AtIWS1 is enriched in transcribed as well as promoter regions of the target genes under BR-induced conditions. Our results suggest that AtIWS1 is recruited to target genes by BES1 to promote gene expression during transcription elongation process. Recent genomic studies have indicated that a large number of genes could be regulated at steps after RNAPII recruitment; however, the mechanisms for such regulation have not been well established. The study therefore not only establishes an important role for AtIWS1 in plant steroid-induced gene expression but also suggests an exciting possibility that IWS1 protein can function as a target for pathway-specific activators, thereby providing a unique mechanism for the control of gene expression.