Biomedical researchers studying aging and cancer are intensely interested in telomeres, the protective caps on the ends of chromosomes. In a new study, scientists at the University of California-Santa Cruz used a novel technique to reveal structural and mechanical properties of telomeres that could help guide the development of new anti-cancer drugs. Telomeres are long, repetitive DNA sequences at the ends of chromosomes that serve a protective function analogous to that of the plastic tips on shoelaces. As cells divide, their telomeres get progressively shorter, until eventually the cells stop dividing. Telomeres can grow longer, however, through the action of an enzyme called telomerase, which is especially active in cells that need to keep dividing indefinitely, such as stem cells. Researchers have also found that most tumor cells show high telomerase activity. Dr. Michael Stone, an assistant professor of chemistry and biochemistry at UC-Santa Cruz, said his lab is particularly interested in the folding and unfolding of a DNA structure at the tail end of the telomere, known as a G-quadruplex, because it plays a key role in regulating telomerase activity. "Most cancer cells use telomerase as one mechanism to maintain uncontrolled growth, so it is an important target for anti-cancer therapeutics," Dr. Stone said. "The G-quadruplex structures of telomere DNA inhibit the function of the telomerase enzyme, so we wanted to understand the mechanical stability of this structure." Xi Long, a graduate student in Dr. Stone's lab, led the project, which involved integrating two techniques to manipulate and monitor single DNA molecules during the unfolding of the G-quadruplex structure.
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