Research

The LeBlanc Physics Lab applies an interdisciplinary approach that includes physics, biochemistry, biophysical chemistry, physical chemistry, and nanoscale science to investigate how enzymes carry out biological processes and the molecular details of essential pathways. Our lab seeks to understand how individual proteins interact with their binding partners, how dynamic conformational changes influence those relationships, and how enzymes fail in complex diseases like cancer, particularly Lynch syndrome. 

The LeBlanc Physics Lab would like to thank the following sponsors:

Current Projects 

Ribosome Assembly

Ribosomes are macromolecules that are the sites of essential protein synthesis, made up of RNA and ribosomal proteins assembled into small and large subunits. Successful ribosome assembly involves over 200 enzymes and accessory factors, and must precede protein biosynthesis. Defective ribosome assembly and function leads to rare ribosomopathies and an elevated cancer risk. 

Although essential intermediates in the pathway have been identified, such as Nsa1/WDR74 and Rix7/NVL2, identifying the network of direct interactions between individual factors in the pathway remains an ongoing challenge. Rix7 is an essential enzyme that has been proposed to use the power of ATP binding and hydrolysis to unfold Nsa1 and strip it from large particles in the assembly process. Our lab seeks to understand how precisely Rix7 is driven by ATPase activity and if Nsa1 is the primary substrate. Uncovering the molecular details of Rix7 conformational changes and its dynamic interactions with other factors will provide a starting point for us to tackle the bigger question of how failures in the ribosome assembly pathway lead to disease? 

This project is sponsored by the CZI Science Diversity Leadership Award and is a collaboration with Dr. Robin Stanley at NIEHS. 

DNA Mismatch Repair 

The main goal of this project is to understand how the conformational changes in DNA mismatch repair enzyme MutL, a protein with intrinsically disordered regions, are regulated by ATP binding and hydrolysis, and how its action is impacted when cancer-associated mutations are introduced. 

This project is sponsored by National Cancer Institute K01CA218304.  

SARS-CoV-2 Viral RNA Processing

We designed a single-molecule FRET-based technique to monitor the cleavage of SARS-CoV-2 genetic material (RNA) by a nonstructural protein (Nsp) encoded in its genome. Nsp15 is the 15th cleavage product of the coronavirus-encoded polyprotein pp1ab, which is translated by host ribosomes and cleaved by viral proteases. The replication strategy of CoVs generates long double-stranded RNA (dsRNA) intermediates and polyuridine (PUN) RNA. Humans host dsRNA and PUN RNA sensors that can alert the immune system to a virus invasion. Nsp15 with its preference for cleaving 3’ of uridine (U) is thought to limit the length and abundance of PUN RNA to suppress the host immune response and contribute to coronavirus pathogenesis. 

This activity distinguishes Nsp15 as an intriguing therapeutic target, as opposed to existing treatments that target surface structural proteins to prevent virus entrance into the host. High-resolution cyro-EM reconstructions reveal what Nsp15 looks like structurally before and after cleavage, but no intermediate steps in the cleavage process have been identified. Through this project, we seek to answer how Nsp15 cleaves its target particularly to better understand how to inhibit its activity. 

This project is a collaboration with Dr. Robin Stanley at NIEHS. 

Selected Publications

A practical guide to time-resolved fluorescence microscopy and spectroscopy Benjamin S. Clark, Irene Silvernail, Kenya Gordon, Andi N. Morgan, Lewis A. Rolband, Jose F. Castaneda, Sharonda J. LeBlanc, bioRxiv, (2024), doi: 10.1101/2024.01.25.577300

Coordinated protein and DNA conformational changes govern mismatch repair initiation by MutS Sharonda J. LeBlanc, Jacob W. Gauer, Pengyu Hao, Brandon Case, Miho Sakato, Manju M. Hingorani, Keith R. Weninger, Dorothy A. Erie, Nucleic Acids Research, (2018), doi: 10.1093/nar/gky865

Single molecule FRET: A powerful tool to study intrinsically disordered proteins Sharonda J. LeBlanc, Prakash Kulkarni, Keith R. Weninger, Biomolecules, (2018), doi: 10.3390/biom8040140

Using Atomic Force Microscopy to Characterize the Conformational Properties of Proteins and Protein-DNA Complexes That Carry Out DNA Repair Sharonda LeBlanc, Hunter Wilkins, Zimeng Li, Parminder Kaur, Hong Wang, Dorothy A. Erie, Methods in Enzymology, (2017), doi: 10.1016/bs.mie.2017.04.004

Single Molecule FRET to Measure Conformational Dynamics of DNA Mismatch Repair Proteins Jacob W. Gauer, Sharonda LeBlanc, Pengyu Hao, Ruoyi Qui, Brandon Case, Miho Sakato, Manju M. Hingorani, Dorothy A. Erie, Keith R. Weninger, Methods in Enzymology, (2016), doi: 10.1016/bs.mie.2016.08.012

Fluorescence Modulation in single CdSe quantum dots by moderate applied electric fields Sharonda J. LeBlanc, Mason R. McClanahan, Tully Moyer, Marcus Jones, Patrick J. Moyer, Journal of Applied Physics, (2014), doi: 10.1063/1.4856315

Enhancement of Multiphoton Emission from Single CdSe Quantum Dots Coupled to Gold Films Sharonda J. LeBlanc, Mason R. McClanahan, Marcus Jones, Patrick J. Moyer, Nano Letters, (2013), doi: 10.1021/nl400117h