Ring-structured DNA and RNA as key players in Vivo and in Vitro

Abstract

Ring-structured DNA and RNA exhibit a variety of unique features in chemistry, biology, medicine, material science, and so on, which cannot be accomplished by their non-cyclic counterparts. In this review, both naturally occurring DNA/RNA rings and artificially synthesized ones have been comprehensively covered, mainly to bridge these two growing fields. In the first part, the structures and functions of naturally occurring DNA/RNA rings (extrachromosomal circular DNA, circulating cell-free DNAs, cyclic RNAs, and others) are described. Their roles as biomarkers for disease diagnosis are especially noteworthy. The second part mainly presents recent methods to synthesize DNA/RNA rings selectively and efficiently from oligonucleotide fragments. DNA/RNA rings of desired sequences and sizes are successfully prepared in large amounts for versatile applications. Production of RNA rings in cells using autocatalytic transcripts is also described. Lastly, practical applications of DNA/RNA rings are briefly reviewed. Critical significance of the cooperation of these two areas for further developments, as well as strong potential for interdisciplinary studies, have been emphasized.