The long-term objective of this project is to further elucidate the roles of mechanical forces for chromosomes and chromosomal reactions. Chromosome morphogenesis and dynamics will be examined from this perspective, comparatively for E.coli versus the prophase-to-prometaphase transition of eukaryotic chromosomes. Approaches will focus on high resolution 3D analysis, over time in the cell cycle, in wild-type and """"""""mutant"""""""" situations, in living cells where ever possible. For E.coli, specific issues to be addressed will include the underlying physical and molecular basis for development of the nucleoid's helical ellipsoidal shape/density, the significance of this shape for dynamic chromatin movements, and the possibility that of cell division-related licensing of replication initiation. For eukaryotic chromosomes, the possibility of a meiosis-like intermediate will be explored. In complementary studies, our """"""""beads and bottlenecks"""""""" magnetic micropiston will be used to probe the effects of compression and confinement on nucleoids/chromatin and DNA, including effects of real-time changes in buffer and molecular conditions. The roles of mechanical force for RecA- mediated homology recognition and strand exchange will be examined by parallel single molecule studies. Individual steps will be isolated and studied. The notion that reactions mediated by protein phosphatase PP2A are governed in important ways by the elasticity of its HEAT repeat scaffolding subunit will be further explored. Approaches to be used will include in vitro AFM analysis, in silico molecular dynamics, in vivo studies analysis of the PP2A-mediated response to spindle tension during the second division of meiosis, with budding yeast as an experimental system.

Public Health Relevance

All components of biological systems have intrinsic physical and mechanical properties. The long- term goal of our research is to understand the extent to which these properties play governing roles in directing the complex array of biochemical and structural changes that underlie life. Since strategies for public health depend upon, and are nucleated by, an understanding of basic processes, research from this relatively new perspective is likely to lead ultimately to new approaches and thus to improved human health.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Molecular Genetics C Study Section (MGC)
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Reddy, Michael K
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Harvard University
Schools of Arts and Sciences
United States
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Kleckner, Nancy E; Chatzi, Katerina; White, Martin A et al. (2018) Coordination of Growth, Chromosome Replication/Segregation, and Cell Division in E. coli. Front Microbiol 9:1469
Gutu, Andrian; Chang, Frederick; O'Shea, Erin K (2018) Dynamical localization of a thylakoid membrane binding protein is required for acquisition of photosynthetic competency. Mol Microbiol 108:16-31
Liu, Chenli; Danilowicz, Claudia; Kleckner, Nancy et al. (2017) Single molecule identification of homology-dependent interactions between long ssRNA and dsDNA. Nucleic Acids Res 45:894-901
Gladyshev, Eugene; Kleckner, Nancy (2017) Recombination-independent recognition of DNA homology for repeat-induced point mutation. Curr Genet 63:389-400
Yoon, Sang-Wook; Lee, Min-Su; Xaver, Martin et al. (2016) Meiotic prophase roles of Rec8 in crossover recombination and chromosome structure. Nucleic Acids Res 44:9296-9314
Zheng, Hai; Ho, Po-Yi; Jiang, Meiling et al. (2016) Interrogating the Escherichia coli cell cycle by cell dimension perturbations. Proc Natl Acad Sci U S A 113:15000-15005
Kleckner, Nancy (2016) Questions and Assays. Genetics 204:1343-1349
Gladyshev, Eugene; Kleckner, Nancy (2016) Recombination-Independent Recognition of DNA Homology for Repeat-Induced Point Mutation (RIP) Is Modulated by the Underlying Nucleotide Sequence. PLoS Genet 12:e1006015
Yang, Darren; Boyer, Benjamin; Prévost, Chantal et al. (2015) Integrating multi-scale data on homologous recombination into a new recognition mechanism based on simulations of the RecA-ssDNA/dsDNA structure. Nucleic Acids Res 43:10251-63
Peacock-Villada, Alexandra; Coljee, Vincent; Danilowicz, Claudia et al. (2015) ssDNA Pairing Accuracy Increases When Abasic Sites Divide Nucleotides into Small Groups. PLoS One 10:e0130875

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