Identification of miRNAs involved in cell response to ionising radiation and modeled microgravity

BACKGROUND: Ionizing radiation (IR) can be extremely harmful for human cells since an improper DNA-damage response (DDR) to IR can contribute to carcinogenesis initiation. Perturbations in DDR pathway can originate from alteration in the functionality of the microRNA-mediated gene regulation being microRNAs (miRNAs) small noncoding RNA that act as post-transcriptional regulators of gene expression. In this study we gained insight into the role of miRNAs in the regulation of DDR to IR under microgravity a condition of weightlessness experienced by astronauts during space missions which could have a synergistic action on cells increasing the risk of radiation exposure. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed miRNA expression profile of human peripheral blood lymphocytes (PBL) incubated for 4 and 24 h in normal gravity (1 g) and in modeled microgravity (MMG) during the repair time after irradiation with 0.2 and 2Gy of gamma-rays. Our results show that MMG alters miRNA expression signature of irradiated PBL by decreasing the number of radio-responsive miRNAs. Moreover let-7i* miR-7 miR-7-1* miR-27a miR-144 miR-200a miR-598 miR-650 are deregulated by the combined action of radiation and MMG. Integrated analyses of miRNA and mRNA expression profiles carried out on PBL of the same donors identified significant miRNA-mRNA anti-correlations of DDR pathway. Gene Ontology analysis reports that the biological category of Response to DNA damage is enriched when PBL are incubated in 1 g but not in MMG. Moreover some anti-correlated genes of p53-pathway show a different expression level between 1 g and MMG. Functional validation assays using luciferase reporter constructs confirmed miRNA-mRNA interactions derived from target prediction analyses. CONCLUSIONS/SIGNIFICANCE: On the whole by integrating the transcriptome and microRNome we provide evidence that modeled microgravity can affects the DNA-damage response to IR in human PBL.

背景：电离辐射（IR）对人类细胞具有极大的危害性，因为对电离辐射的不当DNA损伤反应（DDR）可能导致致癌作用的启动。DDR通路中的扰动可能源自微RNA（miRNA）介导的基因调控功能的改变，而miRNA是一种作为基因表达转录后调控因子的微小非编码RNA。在本研究中，我们深入探讨了miRNA在微重力条件下对IR的DDR调控作用，微重力是宇航员在太空任务中经历的失重状态，它可能对细胞产生协同作用，增加辐射暴露的风险。方法/主要发现：我们分析了在正常重力（1 g）和模拟微重力（MMG）条件下，经过0.2和2 Gy伽马射线照射后，外周血淋巴细胞（PBL）在4小时和24小时内的miRNA表达谱。我们的结果显示，MMG通过减少辐射敏感miRNA的数量，改变了照射PBL的miRNA表达特征。此外，let-7i*、miR-7、miR-7-1*、miR-27a、miR-144、miR-200a、miR-598、miR-650等miRNA受到辐射和MMG共同作用而失调。对同一位捐赠者的PBL进行miRNA和mRNA表达谱的集成分析，确定了DDR通路中显著的miRNA-mRNA反相关性。基因本体分析报告称，当PBL在1 g条件下培养时，响应DNA损伤的生物类别富集，而在MMG条件下则不富集。此外，一些与p53通路反相关的基因在1 g和MMG条件下的表达水平存在差异。利用荧光素酶报告基因构建的功能验证实验证实了来自靶点预测分析的miRNA-mRNA相互作用。结论/意义：总体而言，通过整合转录组和微RNA组，我们提供了证据表明，模拟微重力可以影响人类PBL对IR的DNA损伤反应。