Gear Up in Circles

Exosomal circRNAs: biogenesis, effect and application in human diseases

Exosomes have emerged as critical mediators of intercellular communication, both locally and systemically, by regulating a diverse range of biological processes between cells. Circular RNA (circRNA) is a novel member of endogenous noncoding RNAs with widespread distribution and diverse cellular functions. Recently, circular RNAs have been identified for their enrichment and stability in exosomes. In this review, we outline the origin, biogenesis and function of exosomal circRNAs as well as their roles in various diseases. Although their precise roles and mechanisms of gene regulation remain largely elusive, exosomal circRNAs have potential applications as disease biomarkers and novel therapeutic targets.

Circular RNAs: Biogenesis, properties, roles, and their relationships with liver diseases

Circular RNAs (circRNAs) are a class of new-found RNA molecules that have a special covalent loop structure without a 5' cap and 3' tail. Researchers have found that circRNAs may be generated by intron-pairing-driven or lariat-driven circularization. They are cleared up by way of extracellular vesicles. They have some advantages such as stability, conservation, and tissue specificity. By serving as sponges of microRNAs, interacting with long non-coding RNAs, mRNA, or proteins, circRNAs regulate gene expression at transcriptional and post-transcriptional levels and contribute to carcinogenesis. In recent years, circRNAs have been found to be correlated with many cancers including hepatocellular carcinoma, one of the most common cancers with high mortality. This article will first introduce the biogenesis, properties, and functions of circRNAs. Then we focus on the molecular mechanisms underlying some circRNAs, including hsa_circ_0001649, hsa_circ_0005075, and cerebellar degeneration-related protein 1 antisense, on hepatocellular carcinoma metastasis.