Department of Health Sciences, University of Genoa, Genoa, Italy.
Mutat Res. 2011 Dec 1;717(1-2):116-28. doi: 10.1016/j.mrfmmm.2011.07.020. Epub 2011 Aug 26.
Exposure to environmental mutagens results in alteration of microRNA expression mainly oriented towards down-regulation, as typically observed in cigarette smoke. However, the molecular mechanism triggering this event is still unknown. To shed light on this issue, we developed an 'in silico' analysis testing 25 established environmental mutagens (polycyclic aromatic hydrocarbons, heterocyclic compounds, nitrosoamines, morpholine, ethylnitrosurea, benzene derivatives, hydroxyl amines, alkenes) for their potential to interfere with the function of DICER, the enzyme involved in the cytoplasmic phase of microRNA maturation. In order to analyse the binding affinity between DICER and each mutagen, the three-dimensional bioinformatic structures of DICER-RNase III domains and of mutagens have been constructed. The binding affinity of mutagens for each DICER's RNase III domain was estimated by calculating the global contact-energy and the number of intermolecular contacts. These two parameters reflect the stability of the DICER-mutagen complexes. All the 25 mutagens tested form stable complexes with DICER, 20 of which form a complex with DICER A domain, that is more stable than those formed by DICER with its natural substrate, i.e. double strand short RNAs. These mutagens are benzo(a)pyrene diol epoxide, nitroimidazoles, fluorenes, naphthalene, morpholine, stilbenes, hydroxylamines, fecapentenes. In the case of exposure to mutagen mixtures (benzo(a)pyrene-diolepoxide and 4-acetylaminostilbene), synergistic or less than addictive effects occur depending on the docking order of the compounds. A group of 8 mutagens with the highest ability to interfere with this DICER function, was identified by hierarchical cluster analysis. This group included 1-ethyl-1-nitrosourea and 4-nitrosomorpholine. Herein, presented data support the view that mutagens interfere with microRNA maturation by binding DICER. This finding sheds light on a new epigenetic mechanism exerted by environmental mutagens in inducing cell damage.
暴露于环境诱变剂会导致 microRNA 表达的改变，主要表现为下调，这在香烟烟雾中是常见的现象。然而，触发这种事件的分子机制仍然未知。为了阐明这个问题，我们开发了一种“计算机模拟”分析，测试了 25 种已建立的环境诱变剂（多环芳烃、杂环化合物、亚硝胺、吗啉、乙基亚硝脲、苯衍生物、羟胺、烯烃），以研究它们是否有可能干扰 microRNA 成熟过程中细胞质阶段的酶 DICER 的功能。为了分析 DICER 与每种诱变剂之间的结合亲和力，构建了 DICER-RNase III 结构域和诱变剂的三维生物信息学结构。通过计算全局接触能和分子间接触数来估计诱变剂与每个 DICER 的 RNase III 结构域的结合亲和力。这两个参数反映了 DICER-诱变剂复合物的稳定性。所有 25 种测试的诱变剂都与 DICER 形成稳定的复合物，其中 20 种诱变剂与 DICER 的 A 结构域形成复合物，其稳定性高于 DICER 与天然底物双链短 RNA 形成的复合物。这些诱变剂包括苯并（a）芘二醇环氧化物、硝基咪唑、芴、萘、吗啉、二苯乙烯、羟胺、菲。在暴露于诱变剂混合物（苯并（a）芘二醇环氧化物和 4-乙酰氨基二苯乙烯）的情况下，协同作用或低于相加作用取决于化合物的对接顺序。通过层次聚类分析，确定了一组 8 种具有最强干扰 DICER 功能能力的诱变剂。这组包括 1-乙基-1-亚硝脲和 4-亚硝基吗啉。本文提供的数据支持诱变剂通过与 DICER 结合来干扰 microRNA 成熟的观点。这一发现揭示了环境诱变剂通过结合 DICER 诱导细胞损伤的一种新的表观遗传机制。
