Abstract: Here, mainly through solution NMR experiments, we found that the mutant sequence of Thrombin Binding Aptamer (TBA-M) and human telomeric sequence htel3 self-fold into G-quadruplexes in sodium solution, respectively. Appealingly, these two well pre-folded G-quadruplexes can further reassemble into a new heteromolecular G-quadruplex complex (TBA-M/htel3) spontaneously through DNA strand displacement. The stoichiometric ratio between TBA-M and htel3 in the complex is identified as 1∶1. The last three guanosines (G14G15G16) from the 3′-end of TBA-M are involved in the formation of the G-quadruplex core of TBA-M/htel3 complex via Hoogsteen base pairing. In this paper, we reveal for the first time that two well pre-folded G-quadruplexes enable a further Hoogsteen pairing-based DNA strand displacement, in which the reaction process and molecular mechanism are also investigated primarily. Our finding expands the understanding of the interacting pattern and recognition mechanism between differently folded structures of nucleic acids.

Key words: reassembly of heteromolecular G-quadruplex, strand displacement between G-quadruplexes, NMR, CD, DMS footprinting