This project entails the characterization of DNA molecules involved in the processes of DNA recombination.These are typically branched molecules, whose 3D structures are only partially known. A key issue is therecognition of homology by double stranded DNA molecules. We have established that there is an unusual DNAstructure that is formed by homologous molecules when they are in a supercoiled plasmid.
Specific Aim 1. The structure that is formed is a dumbbell-like, where the shaft contains the homologous DNA.We plan to ascertain the structure of the shaft of the homology structure. To see if (as hypothesized) thestructure is indeed PX-DNA, we will proceed v^ath chemically-based experiments, including crosslinking thestrands together andpadlocking the circle. We would like to have the best physical evidence that we can get onthe shaft. The next level of characterization will entail electron microscopic examination of dumbbells that havebeen derivatized by metallic nanoparticles that will be visible. We will use this labeling scheme to try to makethe relevant portions of the dumbbell molecules visible to the cryo-EM, so that those methods can be applied tothis key structure.
Specific Aim 2. We have produced crystals of a variety of branched and otherwise unusual DNA species relevantto recombination. These include designed rhombohedral lattices that self-assemble to form macroscopiccrystals. We plan to determine the structures of these lattices. We also have crystals of the inside of a doublecrossover molecule (related to meiotic intermediates) that diffract to atomic resolution, and a third crystal thatcontains an unusual linkage. We will determine the structures ofthese molecules and will establish their 3Dstructures. In addition, we will try to improve the resolution of some of the larger self-assembling lattices by alashing technique that will, if successful, lead to the ability to insert guests into the lattice.
The presence of homology is central to the key biological processes of genetic recombination and DNArepair. DNA in the cell is capable of assuming many different structures in response to conditions. We havediscovered that in the presence of homology supercoiled DNA (which is the state of DNA in the cell) forrns aspecial structure as a consequence of the homology; we have shown that the structure can be captured bycrosslinking within the cell.
We aim to characterize this structure to the greatest extent possible.
| Jonoska, N; Seeman, N C (2015) Molecular ping-pong Game of Life on a two-dimensional DNA origami array. Philos Trans A Math Phys Eng Sci 373: |
| Padilla, Jennifer E; Sha, Ruojie; Kristiansen, Martin et al. (2015) A Signal-Passing DNA-Strand-Exchange Mechanism for Active Self-Assembly of DNA Nanostructures. Angew Chem Int Ed Engl 54:5939-42 |
| Ohayon, Yoel P; Sha, Ruojie; Flint, Ortho et al. (2015) Covalent Linkage of One-Dimensional DNA Arrays Bonded by Paranemic Cohesion. ACS Nano 9:10304-12 |
| Ohayon, Yoel P; Sha, Ruojie; Flint, Ortho et al. (2015) Topological Linkage of DNA Tiles Bonded by Paranemic Cohesion. ACS Nano 9:10296-303 |
| Baas, Nils A; Seeman, Nadrian C; Stacey, Andrew (2015) Synthesising Topological Links. J Math Chem 53:183-199 |
| Niu, Dong; Jiang, Hualin; Sha, Ruojie et al. (2015) The unusual and dynamic character of PX-DNA. Nucleic Acids Res 43:7201-6 |
| Rusling, David A; Chandrasekaran, Arun Richard; Ohayon, Yoel P et al. (2014) Functionalizing designer DNA crystals with a triple-helical veneer. Angew Chem Int Ed Engl 53:3979-82 |
| Udomprasert, Anuttara; Bongiovanni, Marie N; Sha, Ruojie et al. (2014) Amyloid fibrils nucleated and organized by DNA origami constructions. Nat Nanotechnol 9:537-41 |
| Li, Dadong; Wang, Xiaojian; Shi, Fubo et al. (2014) Templated DNA ligation with thiol chemistry. Org Biomol Chem 12:8823-7 |
| (2013) Correction. J Am Chem Soc 135:10178 |
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