Carol Greider on her 2009 Nobel Prize for work on chromosomes

Greider figured out that an enzyme called telomerase is what prevents our chromosomes from getting smaller and smaller.

Carol Greider is a molecular biologist at the Johns Hopkins University in Baltimore. Along with two collaborators, Greider won the 2009 Nobel Prize in Medicine for her work on chromosomes.

Carol Greider: Chromosomes are where all the DNA is in the cell that gives the instructions for all the processes that the cell has to undergo. The chromosome is duplicated every time the cell has to divide.

And cell division is what keeps our bodies healthy and growing. Greider explained that, when cells divide, a little material gets sheared off the ends of the chromosomes. About two decades ago, Greider figured out that an enzyme called telomerase is what prevents our chromosomes from getting smaller and smaller.

Carol Greider: The telomerase is an enzyme, sort of like a little machine inside the cell. It balances out the shortening that occurs during cell division.

If cells get too short, she said, they stop dividing altogether. Greider said that telomerase adds special genetic coding onto the ends of chromosomes, to keep them from getting too small after they divide. Since her intial discovery of telomerase, Greider told us, a number of medical applications for it have been found- in helping stop the runaway cell growth associated with cancer, for example.

Carol Greider: If you block telomerase, in certain kind of cancer cells, you can actually stop those cells from dividing.

Greider added that, on the other hand, there are applications for telomerase in longevity research – that is, using telomerase to optimize cell division, so that cells don’t age and die.She explained that the part of the chromosome telomerase effects are the telomeres.

Carol Greider: The telomeres are the end parts on the chromosomes, and they protect the chromosome kind of like a plastic tip protects a shoelace, they protect it from anything that might chew away at the ends.

She said that she first made her discovery about telomeres and telomerase not on humans, but on on protozoa – a paramecium-type organism- the kind you might find in a pond. Greider explained why she chose to work with this tiny creature:

Carol Greider: A single cell of tetrahymena has 40,000 chromosomes. So if you want to find what it is that maintains telomeres, you go to the source- a cell that has 40,000 chromosomes. By contrast, have only 96 chromosome ends, so there’s significantly less. We knew this was a fundamental process and likely to be the same in all cell types, we went for the organism in which we were most likely to be successful in finding what became known as telomerase.

Greider said her research was an example of curiosity-based research – she simply wanted to know more about how living organisms solved the problem of their shortening telomeres. She said her findings can came to have a significance decades after her research, the exact nature of which she couldn’t have known at the outset.

Carol Greider: It was really an example of curiosity driven research. We knew that there was this problem at all cells face that everytime the cells divide, chromosomes shorten a little bit from their ends. And we were just wondering: how do cells solve this problem? Just asking this fundamental questions, we discovered this enzyme, telomerase. We really knew that something so fundamental would have important implications, we just didn’t know what they were. That’s why this is an example of curiosity-driven research that later on, in the intervening 25 years since the discovery, it’s become apparent that there are these very important medical implications of the telemeres and the telomerase, and we can see what roles they play in human disease.

She said that her discovery has practical implications for cancer research, as well as longevity research.

Carol Greider: If you take human cells and put them into culture, they’ll divide for a certain number of times and then they’ll stop dividing. And what we showed was that the telomere shortening that happens progressively every time the cells divide in culture is due to the telomere problem. And we now know that the ability of the cells to divide a certain number of times plays a role in human disease. One example is bone marrow failure. You need cells in your body to renew the blood every day because blood cells don’t live very long. And in the bone marrow there are these cells that divide that allow new blood cells to be made. And in turns out that in families with genes causing too little telomerase, where the telomeres get progressively shorter, people can get very sick and die from bone marrow disease.

Greider told EarthSky about what it was like to win the Nobel Prize.

Carol Greider: The phone rang and they told me that they were calling from Stockholm to say I’d won the Nobel Prize, and my heart went to my throat!

Beth Lebwohl