The Nobel Prize in Physiology or Medicine 2009 was awarded jointly to Elizabeth H. Blackburn, Carol

The Nobel Prize in Physiology or Medicine 2009 was awarded jointly to Elizabeth H. Blackburn, Carol

The Nobel Prize in Physiology or Medicine 2009

Every human being, with all the different cell types and tissues, develops from a single fertilised egg cell by means of repeated cell divisions. The structural map found inside our genetic material is copied in its entirety before each cell division. Each cell needs to carry the complete map inside it.
By the mid-20th century, it was clear that genetic material is made up of DNA strands inside the cell nucleus. These DNA strands are packed into chromosomes, numbering 46 in humans. Two past Nobel Laureates, Hermann Muller and Barbara McClintock, long ago observed that the ends of the chromosomes, which Muller named the telomeres, were special and particularly stable. One unanswered question was: In what way were these telomeres different, and what was their actual function?
Another question: How can telomeres be fully copied? Based on the knowledge that was available in the late 1970s, the DNA in chromosomes should become shorter each time a cell divided. But this is not what actually happens.
The first question − about the function of the telomeres − was answered after Elizabeth Blackburn and Jack Szostak met at a scientific conference in 1980 and began their research collaboration. In a pioneering experiment, they demonstrated that telomere DNA from one organism, a unicellular ciliated protozoan called Tetrahymena thermophila, would protect and stabilise chromosomes in an entirely different organism, yeast. The natural chromosomes in yeast cells were also shown to contain similar DNA sequences with the same function. Today we know that the protective function of telomeres is strongly conserved in the evolutionary chain and is present in all higher organisms, including us humans.
The second question − how telomere DNA could be formed and avoid becoming shorter each time a cell divided − was answered in an elegant way by Elizabeth Blackburn and Carol Greider. They discovered an enzyme that can produce telomere DNA. The very first proof that this enzyme existed came as a fantastic Christmas present, on Christmas Day 1984. The enzyme was given the name telomerase. It turned out to be unique in its structure and to consist of an enzymatically active protein component plus an RNA component that serves as a template for the formation of new telomere DNA.
Knowledge of telomeres and telomerase has led to important medical insights in many different fields.
One group of rare congenital diseases is caused by mutations that impair the functioning of telomerase. These diseases are characterised by bone marrow defects that result in reduced formation of new blood cells and can now be diagnosed with certainty.
If telomeres are not preserved, eventually cells cannot survive. Telomere shortening is thus one of several factors that affect the ageing process. In contrast, cancer cells can divide endlessly and nearly all of them have elevated telomerase activity. There is consequently hope that new drugs which target telomerase can be developed to fight cancer, and a number of clinical trials are under way.
The discovery of the vital role of telomeres in preserving chromosomal and genetic stability was made through research driven by curiosity and aided by simple model organisms. The findings of this research have provided fundamental insights into human biology and disease mechanisms.