Alexis Reyes

Alexis is a 2nd year IBiS student in Yuan He's lab. She received a BS in Biology from Vanguard University. Alexis can be contacted via email here.


Structural and functional insights toward the visualization of human telomere maintenance macromolecular machines

Maintaining genetic integrity is a top priority for all organisms. Eukaryotes experience a unique challenge in protecting their genetic information due to the packaging of DNA into linear chromosomes. The ends of linear chromosomes cannot be replicated by conventional DNA polymerases because de novo synthesis is required. The result is incomplete replication of chromosome ends by conventional replication machinery, known as the end replication problem. The end replication problem was solved with the discovery of telomerase, the protein complex responsible for de novo synthesis of telomeric repeats. These telomeric repeats are critical for the protection of chromosome ends from degradation. Since the discovery of telomerase, work has been done to identify and determine the function of protein complexes responsible for protecting and elongating telomeres. One such protein complex is shelterin, a six subunit complex that binds the double and single stranded regions of telomeres. Shelterin’s presence at telomeres protects against unwarranted DNA damage responses, end-to-end chromosome fusion, and recruits and regulates telomerase activity. Once recruited to telomeres, the telomerase reverse transcriptase (TERT) subunit utilizes the telomerase RNA (TR) subunit as a template to add on telomeric repeats. Despite numerous studies revealing interactions between these complexes, the structures and functions of complete human shelterin and telomerase have yet to be determined.

The goals of my project are to determine the structures of human shelterin and telomerase complexes, to characterize the structural interactions between the complexes, and determine the mechanisms used in telomere elongation and length control. To achieve these goals, I plan on using single particle cryo-electron microscopy (cryo-EM). Cryo-EM allows for the structural characterization of small amounts of heterogeneous samples, which makes cryo-EM an ideal method to study the scarce and dynamic macromolecular machinery associated with telomere maintenance. I plan on determining the structures of shelterin and telomerase by using cell free in vitro translation to reconstitute the complexes, and assemble them on DNA substrates that mimic the telomere regions they bind to. Assembly of shelterin and telomerase on the same DNA substrate will provide insight into how telomerase elongates telomeres and how shelterin monitors the elongation and regulates telomerase activity.


Recent Photos

September 12, 2016