Simple G4 structures of c-Myc and TERRA. (A) Three-tiered, unimolecular G4 structure adopted by a sequence from the c-Myc promoter (PDB:1XAV; Ambrus et al. 2005). (B) Three-tiered bimolecular RNA G4 structure of TERRA (PDB:3IBK; Collie et al. 2011). (C) Schematic of the c-Myc G4, highlighting canonical DNA G4 structural features. The guanines of the G4 are anti, predominantly C2′-endo, and are in an all-parallel connectivity, with mono- and di-nucleotide propeller loops. See Table 1 for code. In all figures, residue numbers correspond to those in the PDB depositions. (D) Schematic of TERRA illustrating canonical RNA G4 structural features. The guanines adopt the anti conformation are connected in a parallel connectivity and are predominantly in the C3′-endo sugar pucker.
