Elizabeth Blackburn is an Australian-American scientist and was awarded the Nobel Prize in Physiology or Medicine in 2009, for her co-discovery in 1984 of telomerase, the enzyme that replenishes the telomere, a structure at the end of chromosomes that protects the chromosome. Blackburn shared the award with Carol W. Greider and Jack Szostak.
Blackburn was born in Hobart, Tasmania, on November 26, 1948. As a young girl, she loved to play with a variety of animals, from chickens and rabbits to jellyfish. This love of animals then grew into a love of biology. Blackburn went on to earn a Bachelor of Science and a Master of Science in the field of biochemistry from the University of Melbourne. 

She continued her studies at the University of Cambridge, earning her PhD in 1975, working with Frederick Sanger, developing methods to sequence DNA using RNA as well as studying the bacteriophage Phi X 174. While at Cambridge, Blackburn met her future husband, John Sedat. Sedat had previously taken a position at Yale and Blackburn decided to finish her postdoctoral there. Blackburn later said; “Thus it was that love brought me to a most fortunate and influential choice: Joe Gall´s lab at Yale.”
At the time Blackburn began her research, it was clear that nucleic acids were crucial to life. It was already known that DNA was packaged in small portions in the cell nucleus, called chromosomes. On the ends of the chromosomes there were some thickenings, known as  caps. Scientists call them telomeres. However, what was not clear to anyone at the time, what was the function of these parts of the chromosomes. Chromosomes are nothing more than multiple DNA wrapped around protein complexes. They do not have their own special membrane that separates them from each other.
Blackburn, working on a protozoan called Tetrahymena thermophila, discovered that these peak, terminal parts of chromosomes consist of certain short, tandemly repeating DNA sequences. Whilst these chromosomes do not encode anything, there are parts that are slightly shortened each time the cell divides. In fact, telomeres have been shown to be the protective “caps” of chromosomes, which protect important parts of DNA – those that encode proteins, while preventing chromosome fusion. However, as telomeres wear out with each new division, this protective cap becomes thinner. This is one of the reasons why our cells, and ourselves, are aging. The chromosomes then become damaged and the DNA does not work perfectly. This leads to a number of diseases, such as cancer, but also organ failure.
Blackburn actually wanted to know what maintains the telomeres of our chromosomes. In 1984, together with her student Carol W. Greider, she discovered telomerase, an enzyme that regenerates telomeres. It is telomerase that protects DNA from stress. These are enzymes that belong to the class of reverse transcriptases and have their own RNA molecule, which is used as a template to extend telomeres. Reverse transcriptases are interesting proteins because they do not use DNA as a template, but RNA.
Telomerases are the “key to youth” and undamaged telomeres. However, if there is too much telomerase, it can lead to the formation of cancer cells. Elizabeth described this as “life on the edge of a knife” – it takes a balance of telomerase expression for our cells to have normal development and cell cycle.

Elizabeth Blackburn remains active in the research of telomeres and the action of telomerase.


Translated by Jonas Helgason

This text was produced with the support of the United States Embassy in BiH as part of the “U.S. Scientists Who Changed the World” project and we thank the US Embassy.
 
 
 
  Author:

Jelena Kalinić, MA in comparative literature and graduate biologist, science journalist and science communicator, has a WHO infodemic manager certificate and Health metrics Study design & Evidence based medicine training. Winner of the 2020 EurekaAlert (AAAS) Fellowship for Science Journalists. Short-runner, second place in the selection for European Science journalist of the year for 2022.