Discovery of a minimalistic DIE-based fluorescent probe for detection of parallel G-quadruplex forms

G-quadruplexes (G4s) are considered to be involved in some key biological processes, leading to the development of a large number of G4 fluorescent probes, which offer possibilities to study G4 dynamics as well as their biological roles. However, the structures of G4s show high polymorphism, which can be classified into parallel, hybrid and antiparallel forms, and the probes targeting a certain topology are limited. In this study, we have developed a minimalistic fluorescent probe by exploiting the disaggregation-induced emission (DIE) principle. The further studies demonstrated that this probe exhibited promising selectivity toward parallel DNA and RNA G4 forms in vitro. Moreover, it was found that this probe could be applied to map the RNA G4s that always form into parallel topologies in live cells, which distinguished it from other reported DIE-based probes that often targeted the mitochondrial or nuclear DNA G4s. To the best of our knowledge, this was the first DIE-based fluorescent probe for mapping cellular RNA G4s.