News Brief by Julia Zubiago
In 1984, Dr. Carol Greider discovered the enzyme telomerase, which helps protect against the shortening of protective caps on the ends of chromosomes. When the protective caps, called telomeres, are shortened, the cell begins to age, and may cause diseases in the lungs and bone marrow. However, overly lengthened telomeres are linked to cancer, since a cell with longer telomeres may divide more times than its usual lifespan and form a tumor. So how do telomeres maintain proper length? Greider says “we’ve known for a long time that telomerase doesn’t tell the whole story of why chromosomes’ telomeres are a given length” (Johns Hopkins Medicine).
Previously, in order to examine whether a protein is involved in maintaining telomere length, the protein needs to be blocked, and the yeast cells are grown in culture for about three months, until detectable differences in telomere length are apparent. This process is not only time consuming, but also limiting, because blocking certain proteins can kill the cells.
Now, a new procedure has been found by graduate student Stella Suyong Lee, who is working in Greider’s lab. She decided to artificially cut mammalian cell’s telomeres, then detect the elongation by telomerase. This test takes less than a day, so it can be performed even if the blocked proteins were needed for cell division. The challenges of working with mammalian cells required years of technical testing, which Lee persevered through. The new test, called addition of de novo initiated telomeres (ADDIT) was used to examine an enzyme called ATM kinase. ATM kinase was blocked using ADDIT, and the results indicated that it was needed to lengthen telomeres. The results were verified by the old, three-month-long telomere test (Johns Hopkins Medicine). The discovery of ADDIT may lead to new understanding about the careful balance between cellular aging and cancer.
Johns Hopkins Medicine. (2015, November 12). Researchers discover other enzyme critical to maintaining telomere length: New method expected to speed understanding of short telomere diseases and cancer. ScienceDaily. Retrieved November 15, 2015 from www.sciencedaily.com/releases/2015/11/151112123159.htm
Stella Suyong Lee, Craig Bohrson, Alexandra Mims Pike, Sarah Jo Wheelan, Carol Widney Greider. ATM Kinase Is Required for Telomere Elongation in Mouse and Human Cells. Cell Reports, November 2015 DOI: 10.1016/j.celrep.2015.10.035