Role of histone modifying enzymes in regulating alternate active versus silent gene expression in plants

这个项目解决了一个研究较少但却很基本的问题，即化学修饰染色体相关蛋白的酶如何在基因表达上引起相反的影响，即激活或沉默基因。遗传和基因组方法的结合将在模式植物拟南芥中应用，以测试这些替代结果来自于协调不同酶的作用的想法。这项研究被整合到教育活动中，包括：为纽约市两所以本科生和少数族裔为主的机构--亨特学院和雷曼学院--的本科生提供研究经验；通过石溪科学和数学教育中心提供的一系列研讨会和暑期讲习班对高中教师进行培训；以及指导博士后研究员在学术界、工业界或联邦政府独立从事职业生涯。翻译后的组蛋白修饰是所有真核生物基因调控的核心，决定着染色质的活性或非活性状态。这些修饰是动态的，受编写器和擦除器的影响，即添加或移除特定官能团的组蛋白修饰酶。此外，一种组蛋白修饰通常促进另一种组蛋白修饰的产生，这一过程称为组蛋白串扰，它塑造了组蛋白修饰的格局及其转录结果。在植物中，组蛋白去泛素酶是一类重要但特性不佳的橡皮擦，与植物生命周期的不同方面有关。这项研究的重点是组蛋白去泛素酶OTLD1，它主要通过与组蛋白H3结合来与染色质结合，并直接与另一种组蛋白修饰酶KDM1C相互作用。OTLD1位于靶基因的启动子区域，令人着迷的是，OTLD1可以抑制和激活其直接靶标。这些发现指出了我们理解中的一个差距：相同类型的组蛋白被相同的组蛋白去泛素化，是如何引起对直接靶基因转录的两种相反影响的，这种能力的生物学意义是什么？这个问题将通过两个特定的目标来解决：(I)确定OTLD1和KDM1C与不同组蛋白变体的关联如何影响由此产生的组蛋白修饰和靶基因的转录调控，以及(Ii)发现KDM1C和/或OTLD1是否通过泛素/蛋白酶体系统下调，并研究这种调控对OTLD1/KDM1C介导组蛋白修饰及其转录结果的影响。这一结果有望促进对染色质水平过程中导致转录抑制或激活的新连接的理解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project addresses a poorly studied, yet fundamental, question of how enzymes that chemically modify chromosome-associated proteins can elicit opposing effects on gene expression, i.e., activating or silencing the gene. A combination of genetic and genomic approaches will be applied in the model plant, Arabidopsis thaliana, to test the idea that these alternate outcomes arise from coordinating the action of distinct enzymes. The research is integrated into educational activities including: research experiences for undergraduate students from two predominantly undergraduate and minority-serving institutions--Hunter College and Lehman College--in New York City; training for high school teachers through a series of seminars and summer workshops offered through Stony Brook's Center for Science and Mathematics Education; and mentoring of a postdoctoral researcher for an independent career in academia, industry, or the Federal government. Post-translational histone modifications are central to gene regulation in all eukaryotic organisms, determining the active or inactive state of the chromatin. These modifications are dynamic, effected by writers and erasers, i.e., histone modifying enzymes that add or remove specific functional groups. Moreover, one histone modification often promotes generation of another, a process termed histone crosstalk, that shapes the histone modification landscape and its transcriptional outcomes. In plants, one major class of important, yet poorly characterized, erasers are histone deubiquitinases, implicated in diverse aspects of the plant life cycle. The study focuses on histone deubiquitinase OTLD1, which is known to deubiquitylate histone H2B, associate with the chromatin mainly by binding to histone H3, and directly interact with another histone modifying enzyme, the histone lysine demethylase KDM1C. OTLD1 is found at the promoter regions of target genes and, fascinatingly, OTLD1 can both repress and activate its direct targets. These findings identify a gap in our understanding: how does deubiquitylation of the same type of histone by the same histone deubiquitinase elicit two opposing effects on transcription of the direct target genes and what is the biological significance of this ability? This question will be addressed by two specific aims: (i) define how association of OTLD1 and KDM1C with different histones variants affects the resulting histone modifications and transcriptional regulation of the target genes, and (ii) discover whether KDM1C and/or OTLD1 are down-regulated via the ubiquitin/proteasome system and study the effects of this regulation on OTLD1/KDM1C-mediated histone modifications and their transcriptional outcomes. The results are expected to advance understanding of new junction in chromatin-level processes leading to transcriptional repression or activation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.