Circular RNA—Is the Circle Perfect?

Abstract

Circular RNA (circRNA) is a distinct class of non-coding RNA produced, in principle, using a back-splicing mechanism, conserved during evolution, with increased stability and a tissue-dependent expression. Circular RNA represents a functional molecule with roles in the regulation of transcription and splicing, microRNA sponge, and the modulation of protein–protein interaction. CircRNAs are involved in essential processes of life such as apoptosis, cell cycle, and proliferation. Due to the regulatory role (upregulation/downregulation) in pathogenic mechanisms of some diseases (including cancer), its potential roles as a biomarker or therapeutic target in these diseases were studied. This review focuses on the importance of circular RNA in cancer.

Practical Significance of Biomarkers in Axial Spondyloarthritis: Updates on Diagnosis, Disease Activity, and Prognosis

“…Circular RNA (circRNA) comprises a different class of noncoding RNA produced; it is a functional molecule with important roles in regulating transcription and splicing, microRNA sponging, and modulating protein–protein interactions. CircRNA can be classified into exonic RNAs (ecircRNAs) , formed by exons, circular intronic RNAs (ciRNAs) , formed by introns, and exon-intron circRNAs (EIciRNAs) , formed by both exons and introns [ 124 ]. More studies have indicated that circRNAs may be associated with the risk of nerve diseases, atherosclerotic vascular diseases, cancer, and autoimmune diseases, suggesting it is a novel diagnostic and prognostic biomarker candidate, as well as a new therapeutic target for different disorders [ 125 , 126 , 127 , 128 ].…”

Non-coding RNAs in skin cancers:Biological roles and molecular mechanisms

“…The development of high-throughput sequencing technology has led to the identification of an increasing number of circRNAs ( Kai Wang et al, 2022 ). Most circRNAs originate from exons in the coding regions of genes, whereas others originate from the 3′-UTR, 5′-UTR, introns, intergenic regions and antisense RNAs ( Caba et al, 2021 ). CircRNAs are classified into four types, namely, exonic circRNAs (ecircRNAs), circular intronic RNAs (ciRNAs), exonic-intronic circRNAs (eiciRNAs), and tRNA intronic circRNAs (tricRNAs) ( Wenqing Zhang et al, 2021 ).…”

MiRNAs and circRNAs for the Diagnosis of Anthracycline-Induced Cardiotoxicity in Breast Cancer Patients: A Narrative Review

“…NcRNAs include, among others, also circular RNAs (circRNAs) [ 15 , 16 ] and long non-coding RNAs (lncRNAs) [ 17 ] that can be aberrantly expressed in various diseases. CircRNA are molecules produced as covalently closed continuous loops that lack 3′- and 5′-ends and, therefore, have a higher tolerance to degradation by RNase R exonuclease [ 15 ].…”

“…CircRNA are molecules produced as covalently closed continuous loops that lack 3′- and 5′-ends and, therefore, have a higher tolerance to degradation by RNase R exonuclease [ 15 ]. They can be classified based on their origin as exonic circRNA (ecircRNA), if they are produced by exon splicing, circular intronic RNA (ciRNA), if the molecule derives from an intronic region splicing, exon-intron circRNA (EIciRNA), if the splicing process regards both exons and introns [ 16 ].…”