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Does the tan come in a delay? Say thank you

Revealing the mechanism that delays the appearance of tanning could help create treatments that will protect us from skin cancer

Here is a familiar phenomenon: we were at the sea, enjoying the sun (we applied sunscreen of course), and only a few hours later our skin changed color. A new study by Tel Aviv University sheds light on the scientific mystery: why the tanning process of the body does not happen immediately, but only hours or even days later. The research findings reveal the mechanism behind the phenomenon, according to which the body first seeks to repair the DNA damage and therefore inhibits the mechanism responsible for skin pigmentation, i.e. tanning.

The research was conducted under the leadership of doctoral student Nadav Alkoshi and Prof. Carmit Levy from the Department of Human Genetics and Biochemistry, The Sackler Faculty of Medicine, and in collaboration with a number of other researchers from the university, the Wolfson Medical Center, the Weizmann Institute of Science, the University of California and the University of Paris-Sacalla. The study was published in the Journal of Investigative Dermatology from Nature.

"The DNA repair mechanism tells all the other mechanisms in the cell: 'Stop everything and let me work quietly'"

"We have two mechanisms designed to protect the skin from dangerous exposure to UV radiation. The first mechanism repairs the DNA in the skin cells damaged by the radiation, and the second mechanism is responsible for the increased production of melanin, which darkens the skin in order to protect it from exposure to radiation in the future, i.e. tanning," explains Nadav Elkoshi. "In the research, we were able to find out why the tanning phenomenon does not occur immediately when the body is exposed to the sun, but with a certain delay. It turns out that the mechanism that repairs our DNA takes precedence over all other systems in the cell, and in fact temporarily paralyzes the pigmentation mechanism. Only after the cells repair the genetic information as best they can, the cells begin to produce the increased melanin," he adds.

To test their hypothesis, the researchers from Tel Aviv University activated the DNA repair mechanism, both in model animals and in human skin tissues, and the result was a tan, without any UV exposure. "The genetic information must be protected from mutations, so this repair mechanism takes precedence inside the cell during exposure to ultraviolet radiation from the sun," explains Prof. Carmit Levy. "The DNA repair mechanism tells all the other mechanisms in the cell: 'Stop everything and let me work quietly.' One system literally paralyzes the other system, until the repair reaches its peak a few hours after the UV exposure, and only then does the pigment production mechanism come into action."

According to her, in their previous study, the researchers showed that one protein called MITF, which undergoes activation during exposure, is the controller of these two mechanisms. "Here we show that a protein that plays a key role in DNA repair, ATM, activates one mechanism and disables the other, probably to also use the factors of the pigmentation mechanism, with the aim of maximizing the chance of the cell surviving without mutations after exposure to radiation."

"This scientific discovery reveals a molecular mechanism which, through further research, could lead to the creation of innovative treatments that would provide maximum protection for the skin against radiation damage, and even prevent the development of skin cancer in the more distant future," concludes Prof. Levy.

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