Research 

UCSC Research Associate 

Based in Prof. Michael Stone's laboratory, we investigate the mechanism of action of telomerases - enzymes that extend the DNA sequence at ends of the chromosomes to protect against shortening during replication. My role is to assemble the optics for single-molecule microscopy using total internal reflection fluorescence (TIRF) and non-scanning confocal detection. I  also analyze  kinetic data for protein-protein and protein-nucleic acid interactions in several collaborative projects (e.g. MHC antigens and Clock proteins).

My previous research carried out at the University of Leicester, U.K.  focused on the molecular basis of muscle contraction and cell motility, fluorescent proteins, rapid-reaction kinetics and single molecule microscopy.


Photo: Three-color laser optics for fluorescence excitation
Two-color avalanche photodiode detection for confocal single-molecule fluorescence photon counting. An example of the output is shown in the video below. The apparatus is used to study shape changes and dynamics in protein and nucleic acids that are labeled with fluorescent dyes using Förster Resonance Energy Transfer. 

Kinetic simulation of telomerase activity

Telomerase is a reverse transcriptase that extends a repetitive DNA sequence at the ends of chromosomes. This graph represents a kinetic simulation showing the progressive formation and decay of intermediates formed by the addition each nucleotide. The intense peaks labeled B, C and D represent repeat addition processivity where the enzyme resets the RNA template. This is the slowest step in the mechanism and leads to a build up of the preceding product (see Bagshaw et al, 2021).

UCSC publications

Hentschel, J., Badstübner ,M., Choi. J., Bagshaw, C. R., Lapointe, C.P., Wang, J., Jansson, L.I., Puglisi, J.D. and Stone, M.D. (2023) Real-time detection of human telomerase DNA synthesis by multiplexed single-molecule FRET. Biophys. J., 122, 3447-3457. https://www.cell.com/biophysj/fulltext/S0006-3495(23)00471-X

Bagshaw, C.R., Hentschel, J. and Stone, M.D. (2021) The processivity of telomerase: insights from kinetic simulations and analyses. Molecules, 26, 7532. https://doi.org/10.3390/molecules26247532 

Chavan, A. G., Swan, J., Heisler, J., Sancar, C., Erns, D. C., Fang, M., Palacios, J. G., Spangler, R. K., Bagshaw, C. R., Tripathi, S., Crosby, P., Golden, S. S., Partch, C. L. and LiWang, A. (2021) Reconstitution of an intact clock reveals mechanisms of circadian timekeeping. Science 374. 6564, abd4453. https://www.science.org/doi/10.1126/science.abd4453 

Jansson, L. I., Hentschel, J., Parks, J. W., Chang, T. R., Cheng, L., Baral, R., Bagshaw, C. R. and Stone, M. D. (2019) Telomere DNA G-quadruplex folding within actively extending human telomerase. Proc. Nat. Acad. Sci. USA, 116, 9350-9359.  https://www.pnas.org/content/116/19/9350

McShan, A. C., Natarajan, K., Kumirov, V. K., Flores-Solis, D., Jiang, J., Badstübner, M., Toor, J. S., Bagshaw, C. R., Kovrigin, E. L., Margulies, D. H. and Sgourakis, N. G. (2018) Peptide exchange on MHC-I by TAPBPR is driven by a negative allostery release cycle. Nature Chemical Biology 14, 811-820.  https://www.nature.com/articles/s41589-018-0096-2

Long, X., Parks, J. W., Bagshaw, C. R. and Stone, M. D. (2013) Mechanical unfolding of human telomere G-quadruplex DNA probed by Integrated Fluorescence and Magnetic Tweezers Spectroscopy. Nucleic Acids Research, 41, 2746-2 755. https://academic.oup.com/nar/article/41/4/2746/2414803


Stone Group, July 2019