1. Short loop length and high thermal stability determine genomic instability induced by G‐quadruplex‐forming minisatellites
AImino proton spectra of CEB25 and mutants in potassium solution. Except for the CEB25 spectra, recorded in ≥ 20 mM K+ solution, all other spectra were obtained in 1 mM KPi buffer. UV‐derived melting temperatures are shown in brackets. Solvent‐exchange protected imino proton peaks are marked by asterisks. B, CThermal difference spectra (TDS)(B) and CD spectra (C) of CEB25 and mutants in potassium solution. Samples were dissolved in 1 mM KPi buffer at ˜ 4 μM DNA strand concentrations. TDS and CD spectra are in colors associated with those in (A). Spectra plotted in broken lines are originated from native [‐L1(n)1] or poly‐T [L1(n)1T] loop sequences. D–IG4 folding topologies: (D) CEB25 comprising an extended central loop of 9 nt; (E) mutants involving central loops of variable length (n from 1 to 7 nt) and sequence (native loop sequence or poly‐thymine); (F, G) L211(TT) and L112(TT) containing thymine loops of 2 and 1 nt at indicated positions; (H) L212(TT) consisting of two thymine loops of 2 nt and one central thymine loop of 1‐nt; (I) L222(TT) consisting of three thymine loops of 2 nt. Tetrad‐bound guanines and backbones are colored cyan and black, respectively. 1‐nt thymine central loop is in gray; 9‐nt natural central loop, red; 5–7‐nt central loop of native or thymine sequence, red (broken‐line); 1‐, 2‐, and 3‐nt poly‐thymine central loop, orange (broken‐line); 2‐nt thymine side loop, orange.
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EMBO J, Volume: 34, Issue: 12, Pages: , First published: 08 May 2015, DOI: ( /embj )