New technique illuminates DNA helix

DNA

3D-model of DNA

Understanding DNA is critically important: It stores the information that drives how cells work and is increasingly being used in nano- and biotechnology applications. One key question for DNA researchers has been what role the helical nature of DNA plays in processes that take place on DNA.

As a motor protein moves forward along DNA, it must twist or rotate the DNA, and therefore work against the torsional resistance of the DNA. (These motors can carry out gene expression or DNA replication as they move along DNA.) If a motor protein encounters too much resistance, it may stall. While scientists know that DNA torsional stiffness plays a crucial role in the fundamental processes of DNA, measuring torsional stiffness experimentally has been exceedingly difficult.

Intuitively, it seems that DNA will become extremely easy to twist under an extremely low force. In fact, many people have made this assumption. We found that this is not the case, both experimentally and theoretically. The technique also offers new opportunities to study twist-induced phase transitions in DNA and their biological implications. Many colleagues commented to me that they were really excited about this finding as it has broad implications for DNA processes in vivo.

 Xiang Gao et al, Torsional Stiffness of Extended and Plectonemic DNA, Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.127.028101

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