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Your Environment. Your Health.

Using New Tools to Study Telomere Damage and Functions

Patricia Opresko, Ph.D.

October 3, 2019

Patricia Opresko, Ph.D.

Opresko works at the interface between several scientific disciplines to study telomere structures and functions.
(Photo courtesy of Patricia Opresko)

Patricia Opresko, Ph.D., is developing cutting-edge technologies that cross scientific disciplines to study DNA damage and repair in telomeres. Telomeres are protective segments at the ends of each strand of DNA, like caps on the end of shoelaces, that get shorter with aging and contribute to uncontrolled growth of cancer cells. Opresko and colleagues developed an innovative tool that combines optical, chemical, and genetic technologies to target damage in telomeres to study downstream effects, telomere functions, and DNA repair.

Telomeres are only a tiny fraction of the total DNA in a cell but they play important roles in cell functions. When telomeres are lost or damaged, cells age more rapidly and stop dividing. In cancer cells, telomeres do not shorten, allowing cells to divide indefinitely. Her long-term research goals are to develop novel strategies that preserve telomeres in healthy cells to prevent aging-related diseases, or that conversely target telomeres in cancer cells to arrest cancer growth.

Breakthrough Tool for Studying Telomere Damage and Repair

the process where light triggers FAP to create the 8-oxoG lesion in the telomere

This diagram shows the process where light triggers FAP to create the 8-oxoG lesion in the telomere.
(Photo courtesy of Patricia Opresko)

Opresko worked with her postdoctoral fellow Elise Fouquerel, Ph.D., chemist Marcel Bruchez, Ph.D., and colleagues in chemical biology, genetics, and molecular biology to develop a highly innovative tool that uses small molecule probes and light to cause highly specific damage. The tool, which creates targeted oxidative stress, has been used to selectively cause damage in the telomere regions of DNA, and, in work with Ben Van Houten, Ph.D., to cause damage in mitochondria, the powerhouse of the cell. Van Houten is a co-investigator with Opresko on an NIEHS-funded mitochondrial damage project.

Oxidative stress occurs when the amount of reactive oxygen species (ROS), either from environmental exposures or from internal factors, exceeds the cell’s ability to protect itself from damage, and accelerates telomere shortening. ROS contain a form of oxygen that easily reacts with other molecules such as DNA, RNA, and proteins. “When people study oxidative stress in entire cells, all kinds of things can happen. You don’t know exactly what causes the telomeres to shorten faster,” according to Opresko.

Opresko’s team sought to limit oxidative damage to telomeres. They linked the telomere-binding shelterin protein TRF1 to a fluorgen-activating peptide (FAP) which binds a photosensitizer dye that produces reactive singlet oxygen locally when activated by red light. The tool also contains a tag for visualizing where it binds on chromosomes using microscopy. Opresko used this tool to induce 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxoG), a common DNA lesion caused by oxidative stress, in telomeres using human cancer cells as a model.

Cells recovered from damage after one treatment, whereas chronic telomeric 8-oxoG induction led to telomere shortening and loss, genomic instability, and reduced cell growth. By limiting oxidative base damage to telomeres, the study shows that telomeric 8-oxoG accumulation directly drives disruptions of telomere and cellular functions.

The direct determination of cause and effect is one of the most exciting outcomes of this project. “This technology is transformative because targeting well-defined base damage to telomeres allows us to unequivocally attribute changes and health outcomes to the telomere damage, eliminating confounding effects of damage elsewhere,” said Opresko.

Picture of telomere structure at the end of chromosomes

Opresko's team uses a Nikon Ti-E Perfect Focus Live Cell Imaging System to visualize telomeres (green) at the ends of chromosomes (blue).
(Photo courtesy of Patricia Opresko)

Visualizing Telomere Structure and Integrity

Opresko’s team also uses cutting-edge technologies to visualize telomere structure and chromosome integrity. For example, they use fluorescent probes with a live-cell imaging system and high-resolution microscopes. Opresko collaborates with colleagues at the Center for Nucleic Acids Science and Technology at Carnegie Mellon University and the Center for Biological Imaging at the University of Pittsburgh to access the best and latest technologies to gather high-resolution data.

Her team also studies proteins and other components of the molecular machinery that repairs DNA damage. For example, she collaborates with several biophysics labs to conduct single-molecule studies with purified proteins to understand how they bind and function at telomeric DNA.

Group photo of Ryan Barnes, Patricia Opresko, Fouquerel, and Samantha Sanford

Postdoctoral fellow Ryan Barnes, Ph.D. (far left), Opresko (left of center), Fouquerel (right of center), and graduate student Samantha Sanford (far right) at the 2019 Cold Spring Harbor Laboratory Meeting on Telomeres and Telomerase, in front of a DNA sculpture.
(Photo courtesy of Patricia Opresko)

Recognitions for Outstanding Research

Opresko is a professor of environmental and occupational health, pharmacology, and chemical biology at the University of Pittsburgh. In 2006, she received the prestigious NIEHS Outstanding New Environmental Scientist Award (ONES) award, which aims to cultivate future environmental health research leaders early in their careers. “By having a solid funding base, it freed up time to develop my research program,” said Opresko. She also enjoyed networking at the annual NIEHS ONES grantee meetings. “The meetings provided me with valuable interactive opportunities with other researchers to foster my career in environmental health,” she said. Opresko was recognized for her cutting-edge work to understand how harmful genotoxic exposures alter telomeres.

In recognition of her outstanding and prolific research career, Opresko was recently awarded a prestigious NIEHS Revolutionizing Innovative, Visionary Environmental Health Research (RIVER) grant with a perfect score on her grant review. The RIVER program is the centerpiece of an emerging effort to support people, not projects, allowing outstanding researchers increased scientific flexibility and stability in funding. “The RIVER award gives me the flexibility to pursue the most promising and fruitful science and discoveries as the project evolves,” said Opresko. With the award, Opresko will expand her work to target telomere damage to specific organs and tissues including studies in animal models. Opresko commented that, “if we can preserve our telomeres in healthy cells, we can prevent aging-related degenerative diseases and cancer.”

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