The discovery of a biological gatekeeper that prevents genetic code from fraying with age has won three American scientists this year’s Nobel prize for medicine.
The award — and the R9-million prize money — is shared by Elizabeth Blackburn (60), Carol Greider (48) and Jack Szostak (56).
It is the first time the foundation has honoured two women at once. The medicine prize has been awarded to 10 women since it was established in 1901.
The researchers identified one of the most critical processes in living organisms, with deep implications for understanding ageing, cancers and inherited diseases.
Blackburn, a University of California biochemist, made headlines once before when she was fired from former president George W Bush’s council on bioethics for criticising his opposition to stem cell research.
Greider, a geneticist at Johns Hopkins University in Baltimore, was Blackburn’s student when the two made their discovery. Szostak was born in London and grew up in Canada, joining the Harvard Medical School in 1979.
Their experiments solved one of the great mysteries of biology, showing how cells copy their chromosomes when they divide.
The first breakthrough came when Blackburn was studying chromosomes in a pond-dwelling organism called tetrahymena. She noticed that at the end of each of the creature’s chromosomes was a repeating DNA sequence, spelt out by the letters CCCCAA.
Her work caught the eye of Szostak, who had developed ‘mini-chromosomes” from DNA strands and was investigating what happened when he injected them into yeast cells. Each time the cells divided, the mini-chromosomes degraded, until they vanished.
The two joined forces to make mini-chromosomes with the CCCCAA sequences at either end. When these were injected into yeast, the DNA sequence protected the chromosomes when they were copied. The researchers called the genetic caps “telomeres”, meaning “end part”.
In 1984 Greider discovered telomerase, the enzyme that makes telomeres. Further studies revealed that healthy telomeres delay ageing in cells, prompting research into potential anti-ageing treatments. —