Rare quadrilateral snail DNA found in living human cells by flashing probes

The DNA structure of a quadruple coil. Loan Imperial College London

New probes allow scientists to see four chains DNA: Interaction with molecules inside living human cells, revealing its role in cell processes.

DNA usually forms a classic double helix of two strands twisting around each other. While DNA can create more exotic eggs in test tubes, few are found in real living cells.

“G-quadruplexes play an important role in vital processes, in a number of diseases, but the missing link is in these living cells.” – Ben Lewis

However, it has recently been observed that four strands of DNA, known as G-quadruplex, form naturally in human cells. In a new study published now Nature communications, led by the team Imperial College London Scientists have developed new probes that can see how G-quadruplexes interact with other molecules inside living cells.

G-quadruplexes are found in cancer cells in higher concentrations, so they are thought to play a role in the disease. Investigations into how G-quadruplexes “come out” of certain proteins և may և help բացահայտ identify molecules that bind to G-quadruplexes, leading to potential new drug targets that could disrupt their activity.

Needle in a haystack

One of the heads of the Imperial Department of Chemistry, Ben Lewis, said: “Another strand of DNA will have a huge impact on all the processes involved, such as reading, copying or expressing genetic information.

“Evidence has already been established that G-quadrants play an important role in life processes, a number of diseases, but the missing link is in these living cells.”

G-quadruplexes are rare inside cells, which means that standard techniques for detecting such molecules are difficult to detect specifically. Ben Lewis describes the problem as “how to find a needle in a haystack, but the needle is made of grass.”

To solve the problem, researchers from the Vilar և Kuimova group at the Imperial Department of Chemistry teamed up with the Vannier Group from the Medical Research Council London Institute of Medical Sciences.

Fluorescence map Nuclear DNA

A microscopic map of daytime running light of nuclear DNA in living cells stained with a new probe. Colors represent the luminosity of 9 (red) և 13 (blue) nanoseconds. Loan Imperial College London

They used a chemical probe called the DAOTA-M2, which illuminates in the presence of G-quadrants, but instead of controlling the brightness of the fluorescence, they controlled how much daylight was in that daylight. This signal does not depend on the concentration of the probe or G-quadrants, which means that it can be used to uniquely represent these rare molecules.

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

Look straight into the living cells

The team used their probes to study the interaction of G-quadruplets with two helical proteins, molecules that “strain” DNA structures. They showed that if those helicase proteins were removed, there would be more G-quadruplets, showing that the helicases play a role in depleting and thus breaking the G-quadruplets.

“Many researchers have been interested in potential drugs for G-quadruplex-binding molecules as potentially cancer-like drugs. “Our method will help make progress on these possible new drugs.” – Professor Ramon Villar

Dr. Jean an-Baptiste Vanier, MRC’s London Institute of Medical Sciences ուտ Institute of Imperial Clinical Sciences, said: “In the past, we had to rely on the indirect effects of these helicases to look at them directly inside living cells.”

They also studied the ability of other molecules to interact with G-quadruplets in living cells. If a molecule inserted into a cell binds to this structure of DNA, it will move the DAOTA-M2 probe, reducing its lifespan, that is, how much luminescence it gives.

This allows us to study the interactions inside the nucleus of living cells, to better understand more molecules, such as atmospheric fluorescents, that cannot be seen under a microscope.

Professor Ramon Villar, from the Department of Chemistry at Imperial, explained: “Many researchers have been interested in the potential cure for G-quadruplex-binding molecules as cancer-like diseases. “Our method will help make progress on these possible new drugs.”

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

The three groups intend to continue working together to improve the properties of their probe, to explore new biological problems, and to shed more light on the role of G-quadruplets in our living cells. The study was funded by the Imperial’s Excellence Fund for Border Studies.

Reference. Peter A. Summers, Benjamin W. Lewis, Jorge Gonzalez-Garcia, Rosa M. Porreca, Aaron HM Lim, Paolo Cadinu, Nerea Martin-Pintado. , David J. Mann, Joshua B. Edel, Jean Baptiste Vannier, Marina K. Kuimova and Ramon Vilar, January 8, 2021, Nature communications,
DOI: 10.1038 / s41467-020-20414-7:

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