New technique illuminates DNA helix

Date:
August 12, 2021
Source:
Cornell University
Summary:
Researchers have identified a new way to measure DNA torsional
stiffness -- how much resistance the helix offers when twisted --
information that can potentially shed light on how cells work.



FULL STORY ========================================================================== Cornell researchers have identified a new way to measure DNA torsional stiffness -- how much resistance the helix offers when twisted --
information that can potentially shed light on how cells work.


========================================================================== 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.

In "Torsional Stiffness of Extended and Plectonemic DNA," published
July 7 in Physical Review Letters, researchers report on a new way to
measure DNA torsional stiffness by measuring how hard it is to twist
the DNA when the DNA end-to-end distance is held constant.

"We figured out a very clever trick to measure the torsional stiffness
of DNA," said senior author Michelle Wang, the James Gilbert White Distinguished Professor in the Physical Sciences in the Department of
Physics in the College of Arts and Sciences and investigator of the
Howard Hughes Medical Institute.

"Intuitively, it seems that DNA will become extremely easy to twist under
an extremely low force," Wang said. "In fact, many people have made this assumption. We found that this is not the case, both experimentally and theoretically." The first author is Xiang Gao, postdoctoral fellow in
the Laboratory of Atomic and Solid State Physics.

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," Wang said.

Yifeng Hong, Fan Ye and James T. Inman, Department of Physics, Laboratory
of Atomic and Solid State Physics, were co-authors on the paper. The
research was supported by funding from the National Institutes of Health
and the Howard Hughes Medical Institute.

========================================================================== Story Source: Materials provided by Cornell_University. Original written
by Linda B. Glaser.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Xiang Gao, Yifeng Hong, Fan Ye, James T. Inman,
Michelle D.

Wang. Torsional Stiffness of Extended and Plectonemic DNA. Physical
Review Letters, 2021; 127 (2) DOI: 10.1103/PhysRevLett.127.028101 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210812092725.htm

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