Tomas Lindahl (born 1938): The Biochemist Who Found That DNA Needs a Repair Crew

Introduction

Tomas Robert Lindahl is a Swedish-born biochemist who spent most of his career in the United Kingdom, at the Imperial Cancer Research Fund (later Cancer Research UK) laboratories at Clare Hall and then the Francis Crick Institute. He is famous for showing that DNA is not a perfectly stable molecule but one that constantly suffers chemical damage, and for discovering the cell's base excision repair system. He shared the 2015 Nobel Prize in Chemistry with Paul Modrich and Aziz Sancar. His work gives the chemical foundation for understanding mutation, ageing and cancer.

Early Life and Family

Lindahl was born on 28 January 1938 in Stockholm, Sweden. He grew up in the Swedish capital and attended school there. As a young man he became interested in medicine and biology, and he decided to study medicine at the Karolinska Institute, one of the leading medical schools in Europe. He has been described by colleagues as private and modest, preferring to talk about experiments rather than his personal life.

Education and Mentors

Lindahl studied at the Karolinska Institute in Stockholm, where he received a medical degree (MD) and a doctorate in 1967 with research on the chemistry of nucleic acids, particularly RNA. After this, he worked as a postdoctoral researcher in the United States, first at Princeton University and then at the Rockefeller University in New York, in a period when molecular biology was developing rapidly. He returned to Sweden in 1970 and joined the University of Gothenburg, where he became a professor of medical chemistry. In Gothenburg he began the experiments on DNA stability that made his name.

Career Timeline

Major Scientific Contributions

Lindahl's main contributions can be summarised in three statements. First, DNA is chemically unstable: it loses purine bases (depurination) and cytosine is deaminated to uracil at rates that matter for a living cell. Second, cells possess enzymes that detect and remove damaged bases; the first was uracil-DNA glycosylase, and this led to the discovery of base excision repair. Third, repair of alkylation damage, involving enzymes such as 3-methyladenine DNA glycosylase and the bacterial Ada system, protects cells from environmental and endogenous alkylating agents. His laboratory at Clare Hall also made contributions to the biochemistry of DNA ligases and nucleases and to the Epstein-Barr virus, which is linked to certain cancers. For the chemistry, see our companion discovery post.

Awards, Honours and Nobel Prize

• Nobel Prize in Chemistry 2015, shared with Paul Modrich and Aziz Sancar, "for mechanistic studies of DNA repair".
• Copley Medal of the Royal Society (2010), one of the oldest scientific awards in the world.
• Fellowship of the Royal Society (elected 1988) and membership of the European Molecular Biology Organization.
• Foreign membership of the US National Academy of Sciences and the Royal Swedish Academy of Sciences.
• Emeritus director of Cancer Research UK's Clare Hall Laboratories and emeritus group leader at the Francis Crick Institute in London.

Personality, Struggles and Lesser-Known Facts

• A chemist's eye on biology. He applied the simple rules of organic chemistry, such as hydrolysis and deamination, to DNA at a time when many biologists thought of it as an inert polymer.
• Surprising numbers. His estimate of thousands of damage events per cell per day was striking at the time, and it became accepted as repair enzymes were discovered.
• Move to the UK. He left Sweden for the UK research environment, where he built the Clare Hall laboratories into a leading centre for DNA repair research.
• Private by nature. He is known for avoiding publicity and for focusing on laboratory work.

Legacy and Influence on Modern Chemistry

Lindahl turned DNA repair from a vague idea into a field of precise chemistry and enzymology. His discoveries explain why mutations happen even without external mutagens, and why all organisms carry repair enzymes. In medicine, understanding of base excision repair led to PARP inhibitors, a class of cancer drugs that exploit repair defects, and to better understanding of how chemotherapy works. The 5-methylcytosine deamination story helps cancer geneticists interpret mutation spectra. His laboratories trained many scientists who now lead research groups around the world.

Lessons for Students

• Test assumptions with simple chemistry. The question "how stable is DNA in water?" led to a Nobel Prize.
• Quantify. Lindahl's careful rate measurements turned a general suspicion into a firm result.
• Follow the logic. If damage occurs, repair must exist; this led him to look for the enzymes.
• Be patient. The significance of his work from the 1970s was fully recognised four decades later.

FAQ

Did Lindahl study chemistry or medicine?

He trained as a physician and biochemist at the Karolinska Institute, but his work is chemical in approach and the Nobel Prize was in Chemistry.

Where did he spend most of his career?

At the Clare Hall Laboratories in Hertfordshire, UK, from 1981, which became part of the Francis Crick Institute.

What was his first major repair enzyme?

Uracil-DNA glycosylase, discovered in 1974.

How does his work connect to cancer drugs?

PARP inhibitors target a repair pathway related to base excision repair and kill tumour cells with defects in other repair genes.

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