The annual Nobel Week in Stockholm began with the announcement of the prize winners in Physiology or Medicine on Monday. The Nobel Committee announced that the 2017 Prize went to researchers Geoffrey Hall, Michael Rosbash and Michael Young for

the discovery of molecular mechanisms that control circadian rhythms - cyclic fluctuations in the intensity of various biological processes associated with the change of day and night.

Life on Earth is adapted to the rotation of the planet. It has long been established that all living organisms, from plants to humans, have a biological clock that allows the body to adapt to the changes that occur during the day in the environment. The first observations in this area were made at the beginning of our era, more thorough research began in the 18th century.

By the 20th century, the circadian rhythms of plants and animals had been studied quite fully, but it remained a secret how exactly the “internal clock” worked. This secret was revealed to the American geneticists and chronobiologists Hall, Rosbash and Yang.

Fruit flies have become a model organism for research. A team of researchers managed to find in them a gene that controls biological rhythms.

Scientists have found that this gene encodes a protein that accumulates in cells during the night and is destroyed during the day.

Subsequently, they identified other elements responsible for the self-regulation of the "cellular clock" and proved that the biological clock works in a similar way in other multicellular organisms, including humans.

The internal clock adapts our physiology to completely different times of the day. Our behavior, sleep, metabolism, body temperature, hormone levels depend on them. Our well-being deteriorates when there is a discrepancy between the work of the internal clock and the environment. So, the body reacts to a sharp change in the time zone with insomnia, fatigue, and a headache. The jet lag syndrome, jet lag, has been included in the International Classification of Diseases for several decades. The mismatch of lifestyle with the rhythms dictated by the body leads to an increased risk of developing many diseases.

The first documented experiments with internal clocks were carried out in the 18th century by the French astronomer Jean-Jacques de Meran. He found that the leaves of the mimosa drop with the advent of darkness and straighten out again in the morning. When de Meran decided to test how the plant would behave without access to light, it turned out that mimosa leaves fell and rose regardless of the light - these phenomena were associated with a change in the time of day.

Later, scientists found that other living organisms have similar phenomena that adjust the body to changes in conditions during the day.

They were called circadian rhythms, from the words circa - "around" and dies - "day". In the 1970s, physicist and molecular biologist Seymour Benzer wondered if the gene controlling circadian rhythms could be identified. He managed to do this, the gene was named period, but the control mechanism remained unknown.

In 1984, Hall, Rooibach and Young managed to recognize him.

They isolated the necessary gene and found that it is responsible for the accumulation and destruction of the protein associated with it (PER) in cells, depending on the time of day.

The next task for the researchers was to understand how circadian fluctuations are generated and maintained. Hall and Rosbash suggested that the accumulation of protein blocks the operation of the gene, thereby regulating the content of protein in cells.

However, in order to block the work of the gene, the protein formed in the cytoplasm must reach the cell nucleus, where the genetic material is located. It turned out that PER does build into the kernel at night, but how does it get there?

In 1994, Young discovered another gene, timeless, that codes for the TIM protein, which is essential for normal circadian rhythms.

He found that when TIM binds to PER, they are able to enter the cell nucleus, where they block the operation of the period gene due to feedback inhibition.

But some questions still remained unanswered. For example, what controlled the frequency of circadian fluctuations? Young later discovered another gene, doubletime, responsible for the formation of the DBT protein, which delayed the accumulation of the PER protein. All of these discoveries have helped to understand how fluctuations are adapted to the 24-hour daily cycle.

Subsequently, Hall, Rooibas and Young made several more discoveries that supplemented and refined the previous ones.

For example, they identified a number of proteins required to activate the period gene, and also uncovered the mechanism by which the internal clock is synchronized with light.

The most likely contenders for the Nobel Prize in this area were virologist Yuan Chang and her husband, oncologist Patrick Moore, who discovered the herpes virus type 8 associated with Kaposi's sarcoma; Professor Lewis Cantley, who discovered the signaling pathways of phosphoinositide-3-kinase enzymes and studied their role in tumor growth; and Professor Carl Friston, who made a major contribution to the analysis of brain imaging data.

In 2016, the winner of the Japanese Yoshinori Ohsumi award for the discovery of the mechanism of autophagy, the process of degradation and processing of intracellular debris.

The Nobel Prize in Medicine and Physiology for 2017 was awarded to three Americans - Jeffrey Hall, Michael Rozbash and Michael Young - for their research on the molecular mechanisms responsible for circadian rhythms, that is, a biological clock with a daily period. The broadcast was conducted on the website of the Nobel Committee.

In 1984, Hall and Rosebash of Brandeis University in Boston and Young of Rockefeller University in New York were working with fruit flies and discovered the period gene, which sets the biological clock. Later, scientists found that this gene codes for the PER protein, which accumulates in the body overnight and is destroyed during the day. So, the researchers came to the conclusion that the level of protein oscillates during the 24-hour cycle.

The Nobel Prize winners suggested that PER inhibits the activity of the period gene, forming a negative feedback loop. The second gene, timeless, which encodes the TIM protein, takes part in this mechanism. The latter binds to PER, and the resulting complex is introduced into the cell nucleus, where it blocks the corresponding DNA. The DBT protein, which is encoded by the doubletime gene discovered by Young, is responsible for the degradation of PER.

“Circadian or circadian rhythms occur in almost every organism on earth. Although the discoveries that won the Nobel Prize were made on Drosophila, the mechanisms of daily regulation are very ancient, and they are implemented in a similar way in very different organisms - such as flowers, insects and mammals, ”explained Forbes the importance of the discovery noted by the Nobel Committee, Head of the Laboratory of Genetic -cell therapy of the Institute of Regenerative Medicine of Moscow State University, Candidate of Medical Sciences Pavel Makarevich. He added that in this way the studies of Hall, Rosebash and Young are also useful for studying the circadian rhythms of people: fatal consequences. These are many new areas of human activity: daily watches, polar regions and, most importantly, space!

The total loss to the American economy from the effects of sleep disorders (including absence from work, accidents at work, and decreased productivity) was estimated at $150 billion as early as 2001. In a RAND study on the impact of lack of sleep on the US economy, losses were estimated at $226 to $411 billion for 2016 depending on the scenario. Japan took second place with an estimated economic loss of $75-139 billion, losses for Germany, Great Britain and Canada were estimated at tens of billions. True, it is worth noting that lack of sleep can be caused by both insomnia and the physical inability to sleep at the allotted time due to a busy schedule.

Thus, the researchers revealed the secret of the “internal clock of cells” and showed how this mechanism functions. Autonomous "internal clock" is necessary to adapt and prepare our body for different phases of the day, it controls sleep, hormonal levels, temperature and metabolism. Correctly working rhythms are important for human health, the authors emphasized. "Their discoveries explain how plants, animals and humans adjust their biological rhythm to synchronize with the rhythms of the Earth," the Nobel Assembly said. Rosebash himself, in an interview with the Howard Hughes Medical Institute in 2014, said that the circadian system determines "susceptibility to disease, growth rate and fruit size." “It affects almost every part of the human body,” the scientist noted.

“After the seminal work of the three laureates, circadian biology has grown into a vast and dynamic field of study that impacts our health and well-being,” the Nobel Prize officials explained. The Nobel Committee is keeping prize winners a closely guarded secret until announced. So, during a press conference at which the recipients of the award were announced, the member of the Nobel Assembly of the Karolinska Institute, which is responsible for awarding the prize, said that when he informed Rosbash that he had received the award, the scientist replied: “You are kidding me.”

The awards ceremony will take place on December 10 - the day of the death of the Swedish entrepreneur and inventor Alfred Nobel. Four of the five prizes bequeathed to him - in the field of physiology or medicine, physics, chemistry and literature - will be awarded in Stockholm. The Peace Prize, according to the will of its founder, is awarded on the same day, but in Oslo. The amount of each award will be 9 million Swedish kronor ($1 million). The prize will be presented to the laureates by King Carl XVI Gustaf of Sweden.

The first Nobel Prize in 2017, which is traditionally awarded for achievements in the field of physiology and medicine, went to American scientists for the discovery of a molecular mechanism that provides all living beings with their own "biological clock". This is the case when literally everyone can judge the significance of scientific achievements, marked by the most prestigious award: there is no person who would not be familiar with the change in the rhythms of sleep and wakefulness. Read about how these watches are arranged and how we managed to figure out their mechanism in our material.

Last year, the Nobel Prize Committee in Physiology or Medicine surprised the public - against the backdrop of increased interest in CRISPR / Cas and oncoimmunology, an award for deeply fundamental work done by methods of classical genetics on baker's yeast. This time, the committee again did not follow the fashion and noted the fundamental work done on an even more classic genetic object - Drosophila. Prize winners Geoffrey Hall, Michael Rosbash and Michael Young, working with flies, have described the molecular mechanism underlying circadian rhythms, one of the most important adaptations of biological beings to life on planet Earth.

What is a biological clock?

Circadian rhythms are the result of the circadian, or biological clock. The biological clock is not a metaphor, but a chain of proteins and genes, which is closed according to the principle of negative feedback and makes daily fluctuations with a cycle of approximately 24 hours - in accordance with the duration of the earth's day. This chain is quite conservative in animals, and the principle of the clock is the same in all living organisms - which have them. Currently, it is reliably known about the presence of an internal oscillator in animals, plants, fungi and cyanobacteria, although some rhythmic fluctuations in biochemical parameters are also found in other bacteria. For example, the presence of circadian rhythms is assumed in bacteria that form the human intestinal microbiome - they are regulated, apparently, by host metabolites.

In the vast majority of terrestrial organisms, the biological clock is regulated by light - so they make us sleep at night, and stay awake and eat during the day. When the light regime changes (for example, as a result of a transatlantic flight), they adjust to the new regime. In a modern person who lives in conditions of round-the-clock artificial lighting, circadian rhythms are often disturbed. According to experts from the US National Toxicology Program, shifted work hours to evening and night hours are fraught with serious health risks for people. Among the disorders associated with disruption of circadian rhythms are sleep and eating disorders, depression, impaired immunity, an increased likelihood of developing cardiovascular disease, cancer, obesity and diabetes.

The human daily cycle: the wakefulness phase begins at dawn, when the body releases the hormone cortisol. The consequence of this is an increase in blood pressure and a high concentration of attention. The best coordination of movements and reaction time are observed during the day. By evening, there is a slight increase in body temperature and pressure. The transition to the sleep phase is regulated by the release of the hormone melatonin, which is caused by a natural decrease in light. After midnight, the deepest phase of sleep normally begins. During the night, body temperature decreases and by morning reaches its minimum value.

Let us consider in more detail the structure of the biological clock in mammals. The higher command center, or “master clock,” is located in the suprachiasmatic nucleus of the hypothalamus. Information about illumination enters there through the eyes - the retina contains special cells that communicate directly with the suprachiasmatic nucleus. The neurons of this nucleus give commands to the rest of the brain, for example, regulate the production of the “sleep hormone” melatonin by the pineal gland. Despite the presence of a single command center, every cell of the body has its own clock. The “master clock” is just what is needed in order to synchronize or reconfigure the peripheral clock.

Schematic diagram of the diurnal cycle of animals (left) consists of phases of sleep and wakefulness, coinciding with the feeding phase. On the right is shown how this cycle is realized at the molecular level - by reverse negative regulation of clock genes.

Takahashi JS / Nat Rev Genet. 2017

The key gears in the clock are the CLOCK and BMAL1 transcription activators and the PER repressors (from period) and CRY (from cryptochrome). The CLOCK-BMAL1 pair activates the expression of genes encoding PER (of which there are three in humans) and CRY (of which there are two in humans). This happens during the day and corresponds to the state of wakefulness of the body. By evening, PER and CRY proteins accumulate in the cell, which enter the nucleus and suppress the activity of their own genes, interfering with activators. The lifetime of these proteins is short, so their concentration drops rapidly, and by morning CLOCK-BMAL1 are again able to activate PER and CRY transcription. So the cycle repeats.

The CLOCK-BMAL1 pair regulates expression not only of the PER and CRY pairs. Among their targets are also a couple of proteins that suppress the activity of CLOCK and BMAL1 themselves, as well as three transcription factors that control many other genes that are not directly related to the work of the clock. Rhythmic fluctuations in the concentrations of regulatory proteins lead to the fact that from 5 to 20 percent of mammalian genes are subject to daily regulation.

And here are the flies?

Almost all of the genes mentioned and the whole mechanism as a whole was described using the example of a fruit fly - American scientists, including the current Nobel Prize winners: Jeffrey Hall, Michael Rosbash and Michael Young, did this.

The life of Drosophila, starting from the stage of hatching from the pupa, is strictly regulated by the biological clock. Flies fly, feed and mate only during the day, and “sleep” at night. In addition, during the first half of the 20th century, Drosophila was the main model object for geneticists, so by the second half, scientists had accumulated sufficient tools for studying fly genes.

The first mutations in genes associated with circadian rhythms were described in 1971 in a paper by Ronald Konopka and Seymour Benzer, who worked at the California Institute of Technology. Through random mutagenesis, the researchers managed to obtain three lines of flies with a violation of the circadian cycle: for some flies, there were as if there were 28 hours in a day (mutation per L), for others - 19 ( per S), and the flies from the third group had no periodicity in behavior at all ( per 0). All three mutations fell into the same DNA region, which the authors called period.

In the mid-80s, Gen. period was independently isolated and described in two laboratories - the laboratory of Michael Young at Rockefeller University and at Brandeis University, where Rosbash and Hall worked. In the future, all three did not lose interest in this topic, complementing each other's research. Scientists have found that the introduction of a normal copy of the gene into the brain of "arrhythmic" flies with a mutation per 0 restores their circadian rhythm. Further studies showed that an increase in copies of this gene shortens the daily cycle, and mutations that lead to a decrease in the activity of the PER protein lengthen it.

In the early 90s, Young's employees received flies with a mutation timeless (Tim). The TIM protein has been identified as a PER partner in the regulation of Drosophila circadian rhythms. It should be clarified that this protein does not work in mammals - its function is performed by the above-mentioned CRY. The PER-TIM pair performs the same function in flies as the PER-CRY pair does in humans - basically repressing its own transcription. Continuing to analyze arrhythmic mutants, Hall and Rosbash found genes clock and cycle- the latter is a mouse analogue of the BMAL1 factor and, together with the CLOCK protein, activates gene expression per and Tim. Based on the results of the research, Hall and Rosbash proposed a model of inverse negative regulation, which is currently accepted.

In addition to the main proteins involved in the formation of the circadian rhythm, a gene for "fine tuning" of the clock was discovered in Young's laboratory - double time(dbt), the product of which regulates the activity of PER and TIM.

Separately, it is worth mentioning the discovery of the CRY protein, which replaces TIM in mammals. Drosophila also has this protein, and it was described specifically on flies. It turned out that if the flies were illuminated with bright light before dark, their circadian cycle shifted slightly (apparently, this also works in humans). Hall and Rosbash's team found that the TIM protein is photosensitive and is rapidly destroyed even by a short light pulse. In search of an explanation for the phenomenon, scientists have identified a mutation cry baby, which canceled the lighting effect. A detailed study of the fly cry gene (from cryptochrome) showed that it is very similar to the circadian photoreceptors of plants already known at that time. It turned out that the CRY protein perceives light, binds to TIM and contributes to the destruction of the latter, thus prolonging the “wakefulness” phase. In mammals, CRY appears to function as a TIM and is not a photoreceptor, but in mice, turning off CRY has been shown, as in flies, to cause a phase shift in the sleep-wake cycle.