Theranostics 2019; 9(2):588-607. doi:10.7150/thno.29678

Review

Circular RNAs in immune responses and immune diseases

Xu Chen1,*, Tian Yang1,*, Wei Wang1, Wenjin Xi1, Tianze Zhang1, Qi Li1, Angang Yang1,✉, Tao Wang2,✉

1. State Key Laboratory of Cancer Biology, Department of Immunology, Fourth Military Medical University, Xi'an, Shaanxi, 710032, P.R. China.
2. Department of Medical Genetics and Developmental Biology, Fourth Military Medical University, Xi'an, Shaanxi, 710032, P.R. China.
* These authors contributed equally to this work.

Abstract

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 5ʹ or 3ʹ 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.

Keywords: circRNAs, biogenesis, function, immune responses, immune diseases

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How to cite this article:
Chen X, Yang T, Wang W, Xi W, Zhang T, Li Q, Yang A, Wang T. Circular RNAs in immune responses and immune diseases. Theranostics 2019; 9(2):588-607. doi:10.7150/thno.29678. Available from http://www.thno.org/v09p0588.htm