Toward a Central Question in Epigenetics: A Major Epigenetic Programming Mechanis

描述 摘要： 表观遗传学代表了生物医学研究的一个令人兴奋的新前沿。表观遗传学中一个核心但基本上尚未探索的问题是，表观遗传调节器如何被引导到基因组中的特定位置，以发挥其功能。已知一些转录因子可以将某些表观遗传因子招募到靶基因的启动子上。然而，到目前为止，这种机制只能解释一小部分基因，以及基因组的一小部分。我实验室最新的果蝇研究表明，PIWI相互作用的RNAs(PiRNAs)在引导表观遗传因子到基因组的许多位置上发挥着重要和直接的作用。特别是，piRNA与PIWI蛋白形成复合体，并直接与基因组中的piRNA互补位置结合，调节它们的表观遗传状态。此外，我们已经证明，PIWI直接招募一个关键的表观遗传因子，称为异染色质蛋白1a到这些位置。基于这些结果，我们提出了“Piwi-piRNA指导假说”，其中Piwi-piRNA复合体作为一种序列识别机制，将表观遗传效应招募到特定的基因组位置来执行表观遗传调控。在这里，我们建议使用遗传学和基因组学相结合的方法来系统地检验这一假说，并在10Basepair分辨率下确定PIWI-piRNA介导的机制对基因组的贡献。具体地说，我们建议：(1)创建第一个功能性表观基因组图谱，以确定PIWI对基因组不同区域的特定表观遗传效应；(2)开发全基因组表观遗传分析，以检查PIWI在调节染色质转录状态方面的充分性和直接作用；以及(3)采取四管齐下的方法，直接测试piRNAs在引导表观遗传因子到其位置的作用。这项拟议的研究应该揭示表观遗传调控的一个有趣的方面，并对表观遗传学、遗传学、分子生物学、发展学等广泛领域产生潜在的变革性影响。

DESCRIPTION Abstract: Epigenetics represents an exciting new frontier of biomedical research. A central yet essentially unexplored question in epigenetics is how epigenetic regulators are directed to specific loci in the genome to exert their function. It is known that a few transcriptional factors can recruit certain epigenetic factors to the promoters of target genes. However, this mechanism so far can only account for a handful of genes, and a tiny fraction of the genome. The latest Drosophila work in my lab suggest that PIWI-interacting RNAs (piRNAs) play a major and direct role in guiding epigenetic factors to many sites in the genome. Particularly, piRNA form complexes with PIWI proteins and directly bind to piRNA-complementary sites in the genome to regulate their epigenetic state. Furthermore, we have shown that PIWI directly recruits a key epigenetic factor called Heterochromatin Protein 1a to these sites. Based on these results, we propose a "Piwi-piRNA guidance hypothesis", in which the Piwi-piRNA complex serves as a sequence- recognition machinery that recruits epigenetic effectors to specific genomic sites to execute epigenetic regulation. Here we propose to use combined genetic and genomic approaches to systematically test this hypothesis and to determine the contribution of the PIWI-piRNA- mediated mechanism to the genome at 10-basepair resolution. Specifically, we propose to: (1) Create the first functional epigenome map to determine the specific epigenetic effect of PIWI towards different regions of the genome; (2) develop a genome-wide epigenetic assay to examine the sufficiency and direct role of PIWI in regulating the transcriptional state of chromatin; and (3) take a four-pronged approach to directly test the role of piRNAs in guiding epigenetic factors to their sites. The proposed study should reveal a fascinating dimension of epigenetic regulation and generate a potentially transformative impact to the broad fields of epigenetics, genetics, molecular, develo