Immunofluorescence microscopy of G-quadruplexes and R-loops

A large variety of non-B secondary structures can be formed between DNA and RNA. In this chapter, we focus on G-quadruplexes (G4) and R-loops, which can have a close structural interplay. In recent years, increasing evidence pointed to the fact that they can strongly influence each other in vivo, both having physiological and pathological roles in normal and cancer cells. Here, we detail specific and accurate methods for purification of BG4 and S9.6 antibodies, and their subsequent use in immunofluorescence microscopy, enabling single-cell analysis of extent and localization of G4s and R-loops.