环状RNA（circ-NR3C1）在膀胱癌中结合miRNA及编码蛋白的双重作用与调控机制研究

Circular RNA (circRNA) is usually stably expressed in a tissue-specific manner. The study on the function and mechanism of circRNA is a new content in the field of gene expression regulation. At present, circRNA is thought to play an important role as an endogenous miRNA sponge. Recent studies have a new understanding of circRNA: circRNA has a potential coding function. We first identified a bladder cancer associated circRNA (circ-NR3C1), which was significantly reduced in bladder cancer, and had an inhibitory effect on growth and invasion of bladder cancer cells. Preliminary studies show that circ-NR3C1 has the dual functions of binding hsa-miR-27a-3p and coding proteins. This study will further reveal the role and underlying mechanism of circRNA-NR3C1/hsa-miR-27a-3p interaction in regulation of Cyclin D1 expression, and clarify the effects of circRNA-NR3C1 encoding protein/FOXO1 complex on inhibition of MMP-2 gene transcription. This work will elucidate both the miRNA sponge and protein encoding roles of the endogenous circRNA, as well as provide a novel strategy for the treatment of bladder cancer.

环状RNA（circRNA）结构稳定、具有组织相关性, 对其功能及作用机制的探讨是基因表达调控研究领域的新内容。目前认为circRNA主要作为内源性miRNA“海绵”发挥作用；新近研究则对circRNA有了新认识：circRNA具有潜在编码功能。我们前期首次鉴定了一种膀胱癌相关circRNA （circ-NR3C1），其在膀胱癌起抑癌作用。初步研究显示：circ-NR3C1具有结合hsa-miR-27a-3p和编码蛋白的双重功能。本研究拟进一步解析circRNA-NR3C1结合hsa-miR-27a-3p对Cyclin D1的表达调控作用及机制，并阐明circRNA-NR3C1编码蛋白结合FOXO1抑制MMP-2转录作用。本项目的成功实施，将从全新的角度阐明circRNA结合miRNA及编码蛋白的双重作用，有望首次揭示人体细胞内源性circRNA编码功能，具有潜在膀胱癌治疗临床应用价值。

环状RNAs（circRNAs）结构相对稳定, 主要通过结合miRNA起调控基因表达的作用、在膀胱癌中的具体作用机制有待进一步阐明，其是否可通过编码蛋白调控膀胱癌的生物学功能也尚不明确。在本研究中，我们首先证实了circNR3C1在膀胱癌组织和细胞系中低表达，且主要定位于细胞浆；体外研究表明circNR3C1可抑制膀胱癌肿瘤生长及转移。在机制上，circNR3C1“海绵吸附”miR-27a-3p，而miR-27a-3p可直接作用于cyclinD1的5’UTR区上调cyclinD1蛋白的表达；同时，我们首次发现circNR3C1在膀胱肿瘤中编码一种全新蛋白，并可抑制MMP-2表达。体内研究结果显示，过表达circNR3C1的膀胱肿瘤中cyclinD1和Ki67的表达较对照组明显降低。此外，我们发现UBAC2在膀胱癌组织及膀胱癌细胞系中的表达均升高，生存分析显示UBAC2在膀胱癌组织中表达与患者的生存期呈负相关；RIP和FISH实验证实，UBAC2可以直接结合circRNA BCRC-3抑制P27表达。本项目从全新的角度阐明circRNA结合miRNA及编码蛋白的双重作用，揭示了内源性circRNA编码功能，具有潜在临床应用价值。