Rare DNA with quadruple helix is ​​found in living human cells with glowing probes

Rare DNA with quadruple helix is ​​found in living human cells with glowing probes

Quadruplicate helical DNA. Credit: Imperial College London

New probes allow scientists to see four-stranded DNA that interacts with molecules in living human cells, unraveling its role in cellular processes.

DNA usually forms the classic double helix shape of two strands wrapped around each other. While DNA may form some more exotic forms in test tubes, little is seen in true living cells.

However, it has recently been seen that four-stranded DNA, known as G-quadruplex, naturally forms in human cells. Now, in new research released today in Nature communicationa team led by scientists from Imperial College London has created new probes that can see how G-quadruple plexus interacts with other molecules in living cells.

G-quadruple plexus is found in higher concentrations in cancer cells, and it is thought to play a role in the disease. The probes reveal how G-quadruple sites are ‘unwrapped’ by certain proteins, and may also help identify molecules that bind to G-quadruple sites, which could lead to new drug targets that could disrupt their activity.

Needle in a haystack

One of the lead authors, Ben Lewis, of the Department of Chemistry at Imperial, said: ” Another form of DNA will have a huge impact on all processes involved – such as reading, copying or expressing genetic information.

“Evidence is increasing that G-quadruple sites play an important role in a wide variety of vital processes, and in a variety of diseases, but the missing link showed this structure directly in living cells.”

G-quadruple plexus is rare in cells, meaning that standard techniques for detecting such molecules are difficult to detect specifically. Ben Lewis describes the problem as “like finding a needle in a haystack, but the needle is also made of hay.”

To solve the problem, researchers from the Vilar and Kuimova groups in the Department of Chemistry in Imperial collaborated with the Vannier group from the London Institute of Medical Sciences of the Medical Research Council.

Rare DNA from quadruplicate helix is ​​found in living human cells with glowing probes

Fluorescence lifetime image microscopy map of nuclear DNA in living cells stained with the new probe. Colors represent fluorescence lifetimes between 9 (red) and 13 (blue) nanoseconds. Credit: Imperial College London

They used a chemical probe called DAOTA-M2, which fluoresces (burns) in the presence of G-quadruple, but instead of monitoring the brightness of fluorescence, they monitored how long this fluorescence lasts. This signal does not depend on the concentration of the probe or G-quadruple plexus, which means that it can be used to visualize these rare molecules unequivocally.

Dr Marina Kuimova, from the Department of Chemistry at Imperial, said: “By applying this more sophisticated approach, we can remove the problems that prevented the development of reliable probes for this DNA structure.”

Look directly into living cells

The team used their probes to study the interaction of G-quadruple sites with two helicase proteins – molecules that ‘unwind’ DNA structures. They showed that if these helicase proteins were removed, more G-quadruple sites were present, indicating that the helicases play a role in the unwinding and thus degrade G-quadruple site.

Dr. Jean-Baptiste Vannier, of the MRC London Institute of Medical Sciences and the Institute of Clinical Sciences at Imperial, said: “In the past we had to rely on indirect signs of the effect of these helicases, but now they look directly into living cells. . ‘

They also investigated the ability of other molecules to communicate with G-quadruple plexus in living cells. If a molecule introduced to a cell binds to this DNA structure, it will displace the DAOTA-M2 probe and reduce its lifespan, i.e. how long the fluorescence lasts.

Through this, interactions within the nucleus of living cells can be studied, and more molecules, such as those that are not fluorescent and cannot be seen under the microscope, are better understood.

Professor Ramon Vilar, from the Department of Chemistry at Imperial, explained: “Many researchers have been interested in the potential of G-quadruplex binding molecules as potential agents for diseases such as cancer. Our method will help advance our understanding of this potential novelty. drugs. ‘

Peter Summers, another lead author of the Department of Chemistry at Imperial, said: “This project was a fantastic opportunity to work on the intersection of chemistry, biology and physics. It would not have been possible without the expertise and close working relationship of all three research groups. ‘

The three groups plan to continue to improve the properties of their sin and to investigate new biological problems and further illuminate the light that G-quadruplexes play in our living cells. The research was funded by Imperial’s Excellence Fund for Frontier Research.


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More information:
Peter A. Summers et al. Visualization of G-quadruplex DNA dynamics in living cells by fluorescence lifelong image microscopy, Nature communication (2021). DOI: 10.1038 / s41467-020-20414-7

Provided by Imperial College London

Quotation: Rare DNA with quadruple helix found in living human cells with glowing sins (2021, January 8) detected on January 8, 2021 from https://phys.org/news/2021-01-rare-quadruple-helix-dna-human- cells .html

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