State Key Laboratory of Cancer Biology, Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, 710032, P.R. China.
Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, Shaanxi, 710032, P.R. China.
Theranostics. 2019 Jan 1;9(2):588-607. doi: 10.7150/thno.29678. eCollection 2019.
Circular RNAs (circRNAs) are novel clusters of endogenous noncoding RNAs (ncRNAs) that are widely expressed in eukaryotic cells. In contrast to the generation of linear RNA transcripts, circRNAs undergo a "back-splicing" process to form a continuous, covalently closed, stable loop structure without 5' or 3' polarities and poly (A) tails during posttranscriptional modification. Due to the widespread availability of several technologies, especially high-throughput RNA sequencing, numerous circRNAs have been discovered not only in mammals but also in plants and insects. Notably, due to their abilities to serve as microRNA (miRNA) "sponges", miRNA "reservoirs", regulate gene expression and encode proteins, circRNAs participate in the development and progression of different immune responses and immune diseases by enriching various forms of epigenetic modification. CircRNAs have been demonstrated to be expressed in a tissue-specific and pathogenesis-related manner during the occurrence of multiple immune diseases. Additionally, because of their circular configurations, expression in blood and peripheral tissues and coexistence with exosomes, circRNAs show inherent conservation along with environmental resistance stability and may be regarded as potential biomarkers or therapeutic targets for some immune diseases. In this review, we summarize the characteristics, functions and mechanisms of circRNAs and their involvement in immune responses and diseases. Although our knowledge of circRNAs remains preliminary, this field is worthy of deeper exploration and greater research efforts.
环状 RNA（circRNAs）是一类新型的内源性非编码 RNA（ncRNAs），广泛存在于真核细胞中。与线性 RNA 转录本的生成不同，circRNAs 在转录后修饰过程中通过“反向剪接”形成连续、共价封闭、稳定的环结构，没有 5' 或 3' 极性和 poly(A) 尾巴。由于多种技术的广泛应用，特别是高通量 RNA 测序技术的发展，不仅在哺乳动物中，而且在植物和昆虫中，都发现了大量的 circRNAs。值得注意的是，circRNAs 能够作为 microRNA（miRNA）“海绵”、miRNA“储库”，调节基因表达并编码蛋白质，通过丰富各种形式的表观遗传修饰，参与不同免疫反应和免疫性疾病的发生发展。circRNAs 在多种免疫性疾病的发生过程中呈现出组织特异性和与发病机制相关的表达模式。此外，由于其环状结构，在血液和外周组织中的表达以及与外泌体的共存，circRNAs 具有内在的保守性以及环境抵抗稳定性，可能被视为某些免疫性疾病的潜在生物标志物或治疗靶点。在这篇综述中，我们总结了 circRNAs 的特征、功能和作用机制及其在免疫反应和疾病中的作用。尽管我们对 circRNAs 的了解仍处于初步阶段，但这一领域值得更深入的探索和更大的研究努力。
