Sadikovic Bekim, Andrews Joseph, Carter David, Robinson John, Rodenhiser David I
London Regional Cancer Program, London Health Sciences Centre, University of Western Ontario, London, Ontario, Canada.
J Biol Chem. 2008 Feb 15;283(7):4051-60. doi: 10.1074/jbc.M707506200. Epub 2007 Dec 7.
Current toxicogenomic approaches generate transcriptional profiles that can identify functional gene expression signatures of environmental toxicants. However, the intricate processes governing transcription are overlaid with a complex set of molecular instructions involving epigenetic modifications. These commands regulate both gene expression and chromatin organization through coordinated sets of histone modifications and heritable DNA methylation patterns. Although the effects of specific environmental toxicants on gene expression are the subject of much study, the epigenetic effects of such compounds are poorly understood. Here we have used human promoter tiling arrays along with chromatin immunoprecipitation to identify changes in histone acetylation profiles because of chemical exposure. Chromatin from cells exposed to the polyaromatic hydrocarbon benzo(a)pyrene was immunoprecipitated with antibodies against acetylated histones. Affymetrix promoter tiling microarrays were probed to generate epigenomic profiles of hypo- and hyperacetylated chromatin localized to gene promoter regions. Statistical analyses, data mining, and expression studies revealed that treated cells possessed differentially acetylated gene promoter regions and gene-specific expression changes. This chromatin immunoprecipitation-on-chip approach permits genome-wide profiling of histone acetylation patterns that can identify chromatin-related signatures of environmental toxicants and potentially determine the molecular pathways these changes target. This approach also has potential applications for profiling histone modifications and DNA methylation changes during embryonic development, in cancer biology, and in the development and assessment of cancer therapeutics.
当前的毒理基因组学方法能够生成转录谱，从而识别环境毒物的功能性基因表达特征。然而，复杂的转录调控过程还叠加了一系列涉及表观遗传修饰的分子指令。这些指令通过组蛋白修饰和可遗传的DNA甲基化模式的协同作用，调控基因表达和染色质组织。尽管特定环境毒物对基因表达的影响是众多研究的主题，但此类化合物的表观遗传效应却知之甚少。在此，我们利用人类启动子平铺阵列结合染色质免疫沉淀技术，来识别因化学物质暴露而导致的组蛋白乙酰化谱的变化。用抗乙酰化组蛋白抗体对暴露于多环芳烃苯并(a)芘的细胞的染色质进行免疫沉淀。用Affymetrix启动子平铺微阵列进行检测，以生成定位于基因启动子区域的低乙酰化和高乙酰化染色质的表观基因组谱。统计分析、数据挖掘和表达研究表明，处理后的细胞具有差异乙酰化的基因启动子区域和基因特异性表达变化。这种芯片上的染色质免疫沉淀方法能够对组蛋白乙酰化模式进行全基因组分析，从而识别环境毒物的染色质相关特征，并有可能确定这些变化所针对的分子途径。这种方法在胚胎发育、癌症生物学以及癌症治疗的开发和评估过程中，对组蛋白修饰和DNA甲基化变化进行分析也具有潜在应用价值。
