文摘
The cKit87up sequence d(5鈥?/sup>AGGGAGGGCGCTGGGAGGAGGG3鈥?/sup>) can form a unique G-quadruplex structure in the promoter region of the human c-kit protooncogene. It provides a peculiar platform for the design of selective quadruplex-binding agents, which could potentially repress the protooncogene transcription. In this study, we examined the binding of a small library of PNA probes (P1鈭扨5) targeting cKit87up quadruplex in either K+- or NH4+-containing solutions by using a combination of UV, CD, PAGE, ITC, and ESI-MS methodologies. Our results showed that (1) P1鈭扨4 interact with the cKit87up quadruplex, and (2) the binding mode depends on the quadruplex stability. In K+ buffer, P1鈭扨4 bind the ckit87up quadruplex structure as 鈥渜uadruplex-binding agents鈥? The same holds for P1 in NH4+ solution. On the contrary, in NH4+ solution, P2鈭扨4 overcome the quadruplex structure by forming PNA/DNA hybrid complexes, thus acting as 鈥渜uadruplex openers鈥?