一组新的环状RNA circHIFs对低氧诱导因子1alpha 的调控及其在前列腺癌中的作用

The existence of circular RNAs (circRNAs) has been recognized for more than three decades, with thousands novel stable circRNAs being identified in humans, but little known about their functions. We have identified a novel group of circRNAs, designated as circHIFs (HIF1a-associated circRNAs) that upregulate hypoxia inducible factor 1a (HIF1a) gene. Based on our experimental data, we propose that circHIFs upregulate HIF1a by the following possible mechanisms: 1.circHIFs may serve as miR-HIFs sponge, acting as competing endogenous RNAs(ceRNAs) ; 2.circHIFs covalently bind to HIF-1a mRNA and then recruit RNA-binding protein (RBP) to stabilize HIF1a mRNA; 3.circHIFs may bind to or recruit histone modifying enzymes and/or transcription factors or both (co-activators). The current project will focus on discovering novel circHIFs and mechanisms of circHIFs regulation. We will also analyze the relationship between dysregulation of circHIF-HIF1a-HIF1a target molecules and prostate cancer cell biology and patient data to investigate its potential clinical use in the future.

环状RNA（circRNA）是近年来被重新认识的一类RNA，人类细胞中新的circRNA及其功能正在不断被发现和研究，但大多数circRNA的表达、功能和作用机制仍不清楚。通过前期工作积累，我们发现并初步鉴定了circHIF这样一组调控HIF1a基因表达的新型的环状RNA，circHIF可能通过以下机制促进转录因子HIF1a表达，参与肿瘤发生与演进：① circHIF通过ceRNA作用在转录后水平促进HIF1a表达； ②circHIF与HIF1a mRNA配对结合，募集相关分子，增强HIF1a mRNA的稳定性；③ circHIF通过“结合/募集组蛋白修饰酶”和/或“结合/募集转录因子”的机制，或二者的协同作用。本课题研究该组新的circHIF对HIF1a的调控机制，剖析circHIF- HIF1a-HIF1a靶分子调控紊乱与前列腺癌细胞生物学行为及临床病理特点的关系。

本项目在课题组前期研究HIF1alpha转录因子调控通路的基础上，通过生物信息学分析和circRNA转录组测序技术，我们发现了HIF1alpha基因转录后可产生一组环状RNA，命名为circHIFs。课题组重点研究circHIFs调控HIF1alpha的分子机制及其在前列腺癌中的作用。本研究发现circHIF2-8/3-10在前列腺癌中高表达，与预后差相关，是新的预后标记。siRNA转染前列腺癌细胞PC-3和DU145，人工敲减circHIF2-8/3-10后，HIF1alpha mRNA和蛋白表达水平明显下降。人工过表达circHIF2-8/3-10后，HIF1alpha mRNA和蛋白表达水平明显升高。circHIF2-8/3-10通过“UGCUUUG”这一miR330结合位点与HIF1alpha竞争性结合miR330，解除miR330对HIF1alpha转录后抑制作用，促进HIF1alpha高表达。circHIF3-10促进HIF1alpha基因启动子区H3K27me修饰和H3ac修饰。circHIF2-8/3-10-miR330调控紊乱是前列腺癌中HIF1alpha高表达的重要机制，该通路的活化可促进前列腺癌细胞增殖、转移和肿瘤血管生成。上述研究成果具有潜在临床应用价值。