Single Molecule Enzymology Group
Bo SunAssociate Professor , PhD, Associate Professor
School of Life Science and Technology
Single Molecule Enzymology, Single Molecule Biophysics
Ensemble studies have contributed tremendously to comprehending biological reactions. However, these studies characterize the average molecular population, and have limited ability in detecting intermediate states or distinguishing heterogeneities. Over the past few decades, single-molecule techniques, including fluorescence resonance energy transfer (FRET), magnetic tweezers (MT) and optical tweezers (OT), have proven to be exceedingly powerful in addressing this knowledge gap. By studying one molecule at a time, these approaches have enabled significant advancement in the understanding of a wide variety of biomolecular systems, especially those involving DNA and associated proteins. Using these single‐molecule techniques, our research interests are focused on understanding the mechanisms of molecular motors in the process of DNA replication, repair, transcription, and editting, such as helicase, polymerase and nuclease.
1. An international research collaboration has shed new light on DNA replication. The collaboration, led by Professor Bo Sun from the School of Life Science and Technology at ShanghaiTech University and Professor Michelle D. Wang from the Howard Hughes Medical Institute (HHMI) and Cornell University, revealed a new replication recovery pathway. Their paper, “Helicase Promotes Replication Re-initiation from an RNA transcript,” was published online in Nature Communications on June 13, 2018. This work reveals a novel pathway of replication re-initiation enabled by the participation of a replicative helicase.
Figure 1. Helicase assists a non-replicating DNAP in bypassing a lesion and displacing a stalled RNAP, in order to re-initiate DNA replication.
2. Research teams led by Professor Sun Bo from SLST and Professor Shen Bin from Nanjing Medical University have completed a high-resolution quantitative map of Cas9/sgRNA/DNA interactions. On November 13, 2019, this work was published as a research article entitled,“The post-PAM interaction of RNA-guided spCas9 with DNA dictates its target binding and dissociation, in the journal Science Advances. This work identifies a critical interaction of Cas9 with DNA that dictates its binding and dissociation, suggesting a distinct strategy to modulate Cas9 activity.
Figure 2. Experimental configuration for single-molecule unzipping experiments and spCas9-sgRNA-DNA interaction mapping.
3. On Feburary 25, 2020, research teams led by Professor Sun Bo from SLST and Professor Xi Xu-Guang from French National Centre for Scientific Research (CNRS) have collaboratively published a research article entitled “Human RPA activates BLM's bidirectional DNA unwinding from a nick” in the journal eLife, revealing a novel unwinding model of a DNA-repair-involved helicase.
Figure 3. A, A schematic of the experimental configuration; B, Representative kymographs of unidirectional and bidirectional DNA unwinding.
4. Research team led by Professor Bo Sun has systemically investigated the molecular mechanism governing DNA binding, unwinding and cleavage by SaCas9. They provide a detailed dynamic understanding of SaCas9 in DNA target association and dissociation. In addition, two stable interactions between SaCas9 and DNA governing their interplay have been identified. On August 13, 2020, this study was published as a research article entitled,“Dynamics of Staphylococcus aureus Cas9 in DNA target Association and Dissociation”, in the journal EMBO Reports.
Figure 4. A, A combination of optical tweezer and confocal microscopy to detect the dissociation of SaCas9 after DNA cleavage; B, Proposed model for SaCas9.
5. On March 30, 2021, Sun lab published a research paper entitled "Proximal single-stranded RNA destabilizes human telomerase RNA G-quadruplex and induces its distinct conformers" in The Journal of Physical Chemistry Letters. Using circular dichroism, nuclear magnetic resonance, single-molecule fluorescence resonance energy transfer, single-molecule optical tweezers and enzymatic digestion assays, this work revealed that the stability and conformation of an RNA G-quadruplex (RG4) forming sequence identified near the end of human telomerase RNA is significantly impaired by its proximal ssRNA. This work provides new insights into the stability and folding dynamics of RG4 that are essential for understanding its biological functions.
Figure 5. A-H, Mechanical stability and accessibility of the RG4-forming sequence detected by optical tweezers and in vitro enzymatic cleavage assays.
Representative Publications (*First Author, # Corresponding Author)
Group Member and Photo