Apt1 competes with RDE, but not CBFβ, for binding to the Runt domain. (A) SPR sensorgrams to analyze the competition between Apt1 and RDE. Following immobilization of the RDE to flow cell 1 on the sensor chip, the Runt domain (50 nM) mixed with 50 nM Apt1, RDE, 30N random RNA, or nothing was injected into flow cells 1 and 2 for 60 sec and dissociated for 180 sec at a flow rate of 20 μL/min. The signals of flow cell 1 were subtracted from that of flow cell 2 to eliminate nonspecific interactions. (B) Comparison of SPR sensorgrams for ternary complex formation between RDE–Runt–CBFβ (left) and Apt1–Runt–CBFβ (right). Following immobilization of the aptamer or RDE to flow cell 1 on the sensor chip, the Runt domain (50 nM) was injected into flow cells 1 and 2 for 60 sec at a flow rate of 20 μL/min. Then, 180 sec after injection of the Runt domain, CBFβ (500 nM) was injected into flow cells 1 and 2 for 60 sec and dissociated for 180 sec. (Arrows) Injection points. The signals of flow cell 1 were subtracted from that of flow cell 2 to eliminate nonspecific interactions, which results in the spikes of noise at the injection points due to the time lag between the flow cells 1 and 2.
