Scientists understand the chemistry involved in gene expression, but they know little about the physics. The U-M group is believed to be the first to actually demonstrate a mechanical effect at work in this process. Their paper is published in the current edition of Physical Review Letters.
"We have shown that small forces can control the machinery that turns genes on and off. There's more to gene regulation than biochemistry. We have to look at mechanics too," said Jens-Christian Meiners, associate professor in the Department of Physics and director of the biophysics program.
A better understanding of how cells regulate themselves could lead to new insights into how the process could fail and lead to disease.
"When cells start to misinterpret regulatory signals, cardiac disease, birth defects, and cancer can result. In fact, mechanical signals have been implicated as a culprit in a variety of pathologies," said Joshua Milstein, a research fellow in the Department of Physics.
To perform their experiment, the scientists used custom "optical tweezers," or lasers, to pull on the ends of bacterial DNA strands with 200 femtonewtons of force, said Yih-Fan Chen, a doctoral student in the Department of Biomedical Engineering. Chen designed and built the tweezers.
The force they used corresponds roughly to the weight of one-billionth of a grain of rice.
In segments of DNA that were tethered to a microscope slide, the scientists observed a 10-fold decrease in the rate at which the strands looped in on themselves.
DNA looping prevents genes within the loops from being expressed. A common mechanism for gene regulation, it also occurs in complex organisms including humans. Specialized proteins act as buckles to connect distant points on the DNA to form the loops. That's the chemistry part. The challenge for physics is to understand how the DNA bends so those distant points can come together.
While this experiment was performed on free DNA, the scientists say forces as much as 100 times stronger are regularly created inside cells as contents shift and buffet each other.
"If we can basically shut this process down with the tiniest force, how could all these larger forces not have an impact on gene expression?" Milstein said.
Meiners and his team are striving for a quantitative understanding of this biological process. He likens the current state of our understanding of gene expression to a diagram. He is searching for equations, and these results begin to provide that.
"We can tell you how long you'll have to wait for a DNA loop to form based on how much force you apply to the DNA," Meiners said. "We're one step closer to understanding cells quantitatively."
The paper is called "Femtonewton Entropic Forces Can Control the Formation of Protein-Mediated DNA Loops."
This research is funded by the National Institutes of Health and the National Science Foundation.
For more information:
Jens-Christian Meiners: http://biop.lsa.umich.edu/meiners-jens-christian.aspx
Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State
What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy