Structural Biology of Tetrahymena Telomerase Interactions at Telomeres

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Telomerase is a special enzyme composed of proteins and RNA that maintains the DNA at the very ends of our chromosomes, called telomeres. Telomerase is a highly regulated determinant of stem cell renewal, aging, and tumorigenesis. In this research project, the PI will investigate the structure and function of proteins that interact with telomerase and telomeres. The project will use telomerase and telomere binding proteins from the model organism Tetrahymena, a ciliated protozoan, which has previously led to basic discoveries. This project will provide essential training for graduate students and postdoctoral fellows in structural biology and biophysics and help them become the next generation of leaders in this multidisciplinary field. This project will also train women, minority, and economically disadvantaged high school, undergraduate, and graduate students to pursue careers in science. Telomerase is an RNA-protein complex (RNP) that extends the 3’ ends of linear chromosomes by repetitively synthesizing the short telomere repeat sequence (TTGGGG in ciliates) using an RNA template embedded in its telomerase RNA (TER) and its specialized telomerase reverse transcriptase (TERT). Telomerase activity at telomeres counteracts the loss of DNA that would otherwise occur during each round of replication. Telomerase is recruited to telomeres and activated by telomere end protection proteins, which otherwise serve to protect telomere ends from being detected as double strand breaks by the DNA damage response. This project will use NMR spectroscopy, X-ray crystallography, cryo electron microscopy (cryoEM), and biochemical methods to investigate the structures and interactions of Tetrahymena telomerase 741 and TEB with p50 and with telomere end-protection proteins, to elucidate their roles in telomeric DNA synthesis, regulation, and end protection. This project is supported by the Molecular Biophysics Cluster of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.