共价封闭的单链环形RNA可以由病毒RNA基因组以及细胞常规非编码RNA和前体信使RNA的加工过程产生。最近的转录组研究惊人地发现，许多编码蛋白质的基因都可以受到回拼，导致一种特定类型的环状RNA（circRNA）在真核细胞中广泛表达。在这里，我们讨论了用于在基因组和个体基因尺度上发现和表征不同circRNA的实验策略。我们进一步强调了目前对circRNA如何生成以及成熟的转录物如何发挥作用的认识。有些circRNA作为非编码RNA发挥作用，通过作为microRNA和蛋白质的诱饵或竞争者影响基因调控。其他形成广泛的核糖核蛋白复合物网络或编码在某些细胞应激的反应中翻译的功能性肽。总的来说，circRNA已经成为基因表达调控中的重要类RNAmolecules，在许多生理过程中产生影响，包括早期发育、免疫反应、神经发生和肿瘤发生。

Covalently closed, single-stranded circular RNAs can be produced from viral RNA genomes as well as from the processing of cellular housekeeping noncoding RNAs and precursor messenger RNAs. Recent transcriptomic studies have surprisingly uncovered that many protein-coding genes can be subjected to backsplicing, leading to widespread expression of a specific type of circular RNAs (circRNAs) in eukaryotic cells. Here, we discuss experimental strategies used to discover and characterize diverse circRNAs at both the genome and individual gene scales. We further highlight the current understanding of how circRNAs are generated and how the mature transcripts function. Some circRNAs act as noncoding RNAs to impact gene regulation by serving as decoys or competitors for microRNAs and proteins. Others form extensive networks of ribonucleoprotein complexes or encode functional peptides that are translated in response to certain cellular stresses. Overall, circRNAs have emerged as an important class of RNAmolecules in gene expression regulation that impact many physiological processes, including early development, immune responses, neurogenesis, and tumorigenesis.