R-loop： an emerging regulator of chromatin dynamics

The dynamic structure of chromatin, which exists in two conformational states： heterochromatin and euchromatin, alters the accessibility of the DNA to regulatory factors during transcription, rep- lication, recombination, and DNA damage repair. Chemical modifications of histones and DNA, as well as adenosine triphospahate-dependent nucleosome remodeling, have been the major focus of research on chromatin dynamics over the past two decades. However, recent studies using a DNA-RNA hybrid-specific antibody and next-generation sequencing approaches have revealed that the formation of R-loops, one of the most common non-canonical DNA structures, is an emer- ging regulator of chromatin states. This review focuses on recent insights into the interplay between R-loop formation and the epigenetic modifications of chromatin in normal and disease states.