Nobel Prize in Chemistry: DNA repairs itself | Science| In-depth reporting on science and technology | DW | 07.10.2015
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Nobel Prize in Chemistry: DNA repairs itself

Our genetic material is constantly being damaged - but little helpers keep on repairing it. Without them, we would die very young. For this discovery three scientists were awarded the Nobel Prize.

In some years, the Nobel Prize committee appears to be rather conservative. This is such a year.

Many experts thought that the new technology of gene editing called CRISPR could be honored with a Nobel Prize in Chemistry this year.

The technique, first published in 2012, is already a big game changer in biology, keeping scientists on their toes around the world. But with its huge potential, pressing concerns also emerge. It is a technology that might enable amazing cures - or devastating misuse, for example by creating designer babies.

Instead, the Nobel Prize committee honored three scientists who made groundbreaking discoveries in biochemistry - decades ago. Tomas Lindahl from Sweden, Paul Modrich from the US and the Turkish-American Aziz Sancar received the award for "the mechanistic studies for DNA repair."

Lindahl is professor emeritus at the Francis Crick Institute and Clare Hall Laboratory in Hertfordshire, UK; Paul Modrich works at the Duke University in Durham, North Carolina, and Aziz Sancar at the University of North Carolina in Chapel Hill.

During their research in the 1960s to 1980s, they discovered proteins which repair damages constantly occuring in our genetic material.

"Life as we know it today is totally dependent on DNA repair," said Sara Snogerup Linse of the Nobel Prize Committee.

The three laureates mapped and explained how cells safeguard genetic information - a discovery that gives insight into how cancer develops.

Long awaited

Aziz Sancar is the first Turkish-born Nobel laureate in the natural sciences.

When asked by Adam Smith, chief of the Nobel media team, if there would be big celebrations in Turkey now, the 69-year old Sancar answered: "Yes, they've been asking over the years and I was tired of hearing 'when are you going to get the Nobel Prize?'"

"It was a surprise," said 77-year-old Tomas Lindahl in a press conference after the Nobel Prize announcement. "I knew for years that I was considered for the prize but so were hundreds of other people."

Lindahl's friend and former colleague Grigory Dianov, now working at the University of Oxford, is "absolutely excited and over the top," he told DW.

In 1990, Dianov came to England from Novosibirsk in the former Soviet Union to work with Lindahl. He just wanted to spend his sabbatical with him - "but then, as you know, the Soviet Union collapsed and I stayed with Tomas Lindahl for three years."

Lindahl was the first to realize that DNA, the molecule that we are all based on, is extremely unstable and needs repair everyday.

"He discovered many mechanisms and many enzymes - he and his colleagues of course," Dianov said. "But he started it all, there's no doubt about it,"

Hazardous environment

Sun radiation, cigarette smoke, drugs, cancerous substances in meat - many things around us can create defects in our genetic material. Experts estimate that thousands of damages occur in our DNA every day.

"Every damage - whatever it is - could become very dangerous," said Karsten Rippe from the German Cancer Research Center in Heidelberg in a DW interview.

Cells whose DNA is altered might degenerate into cancer cells.

To stop that from happening, proteins in our body are constantly looking for mistakes in the DNA to eliminate them.

"There are dramatic consequences if only one component of this repair system is malfunctioning," said Rippe.

An example for this are hereditary diseases - like the Li-Fraumeni syndrome - which lead to one of the many helper proteins being absent.

Patients have a 50 percent risk of developing cancer by age 30. For people whose repair mechanisms work normally, this risk is only one percent.

cancer cell Photo: STEVExGSCHMEISSNER

If the DNA repair is not working, regular cells can easily turn into cancer cells.

One man, one mechanism

In the 1970s, scientists believed that DNA was an extremely stable molecule. But Lindahl demonstrated that DNA decays at a rate that ought to have made the development of life on Earth impossible.

He also found the first type of DNA repair mechanism. Paul Modrich and Aziz Sancar discovered two other kinds of mechanisms. Together, these proteins protect DNA from decaying and make a long life possible.

The three laureates worked parallel and independently from each other. They all got into the field of DNA repair from different sides. Lindahl studied the stability of human DNA, Sancar worked with UV-sensitive strains of bacteria and Modrich examined enzymes.

Modrich got into genetics after his father told him: "You should learn about this DNA stuff." That was in 1963, after James Watson and Francis Crick had been honored with the Nobel Prize in Chemistry for discovering the structure of DNA.

Lindahl, Sancar and Modrich each found 'their" repair mechanism in human cells. But all organisms on Earth, down to bacteria and viruses, have similar strategies to make sure their genetic material stays free of mistakes.

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