Telomeres and Telomerase in Biology
The 2009 Nobel Prize in Medicine was for the Discovery of Telomeres
Oct 7, 2009
Scientists Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak have won the 2009 Nobel Prize in Medicine and Physiology for their work on telomeres and telomerase. Their work focused on the structure, function and implications of telomeres and telomerase in the cell.
What Are Telomeres
Telomeres are repeating units of DNA found at the ends of chromosomes, which don't contain genes. Instead, these repeated structures act as a molecular cap, protecting the chromosomal ends from mutation and shortening. Every time a cell divides, the telomeres at the ends of the chromosomes get shorter, eventually leading to the inability to replicate. Without telomeres, cell division would cut off pieces of actual genes, destroying the DNA's ability to function.
Carol W. Greider and Elizabeth H. Blackburn described their discovery and investigation of telomeres and telomerase in an article "Telomeres, Telomerase and Cancer" featured in Scientific American's February 1996 issue.
How Telomerase Works
Telomerase is an enzyme made of protein and a template strand of RNA that protects against telomere shortening and forms the telomere caps that cover the ends of chromosomes. The template RNA attaches to the ends of chromosomes and forces it to form repeating subunits to attach at the end of the DNA strand, creating the protective cap.
In normal cells, telomerase is active only when the organism is a fetus and small child. As an adult, this enzyme is switched off to prevent uncontrolled growth of the cells. In certain diseases, such as cancer, telomerase is switched on again, which can lead to uncontrolled growth.
There is some indication that telomeres undergo some epigenetic changes. DNA methylation seems to repress telomere construction and the loss of specific epigenetic markers may lead to defective telomere activity, as described in the April 2007 Nature Genetics review paper "The epigenetic regulation of mammalian telomeres" by María A. Blasco.
Why Telomere Shortening is Important
The protective telomere keeps the cell in functioning condition, but when it isn't working correctly there can be serious consequences. In cells with defective telomeres and telomerase, cancer can form. Cancer cells effectively become immortal when telomerase doesn't turn off.
Another aspect of telomere activity scientists study is the effect on aging. Because telomeres shorten over the life of a cell, if scientists could find a way to keep them at a steady length it might lead to halting cell aging.
Future Developments in Telomeres and Telomerase
In the future, scientists who study telomerase have a lot of potential research targets. Some researchers are looking at the evolution of telomeres, comparing these structures to the reverse transcription mechanisms in some viruses.
Companies like Geron and Merck are currently trying to find ways to translate research on telomeres into clinical products to combat cancer and delay the cellular breakdown of aging. A cancer vaccine is one possibility under development.
The importance of telomeres in human biology has been shown in many ways since Dr. Blackburn's team first completed the work that would lead to their 2009 Nobel Prize. Future studies in this area of research have the potential to affect the health of millions.
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