Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

31-POS Board 16 Dynamic Analysis of DNA and Topoisomerase II Interaction Based on Fluorescence Fluctuation and Single Molecule Detection Wan-Chen Huang 1 , Chun-Ying Lee 2 , Tao-Shih Hsieh 1,2 . 1 Academia Sinica, Taipei, Taiwan, 2 National Taiwan University, Taipei, Taiwan. Topoisomerase 2 (Top2) is known as anticancer drug target due to its highly demanded on resolving DNA tangling problems during cell division. These enzymes regulate DNA topology by transiently breaking one DNA double strand (cleavage), allowing the second double strand to pass through the opened DNA gate (opening), and then closing the gate by rejoining the broken end. Previous studies defined the Top2 function mainly at DNA cleavage and re-ligation steps, however, whether the cofactors and Top2 drugs interfere the DNA dynamics at the opening and closing steps remain unclear. Here, we used fluorescence correlation spectroscopy (FCS) and Förster resonance energy transfer (FRET) in combination to examine the cofactor effects on the interaction of Top2 and DNA, and in addition used the single molecule FRET (smFRET) method to observe the opening and closing of DNA gate. Our results demonstrated that both types of anticancer drugs, teniposide (VM26) and dexrazoxane (ICRF187) can interfere the rate of DNA gate dynamics by shortening the dwell time at closing state. Moreover, binding of AMPPNP induced DNA gate dynamics, which is previously unaddressed. These findings unmask the Top2 dynamics after N-gate closure and reveal the potential mechanism of action of Top2 drugs.

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