Molecular mechanism of microbial DNA partitioning : structure and function

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Plasmids in bacterial cells have the centromere-based segregation system to ensure their faithful transmission to daughter cells, and is being studied as a model system for chromosome partitioning mechanism. We studied the general mechanism underlie these plasmid partitioning machineries, and found that SopA and ParA proteins do not directly pull of push plasmid DNA, but rather guide the plasmids to the right direction by making the gradient of protein concentrations. Notably, the gradient of SopA or ParA proteins were formed from the polymerizing center within the cell (SopA forms a filament within the cell, and ParA locates on the nuclear). We have been investigating transmission mechanism of bacterial chromosome as well. As the chromosome transmission guidance protein, we identified novel factor MigP and a component of the complex I of electron transport chain NuoG. both are membrane associating proteins and we expect DNA transmission mechanism could associates membrane localization.DNA checkpoint mechanism in eukaryotic cells stops the cell cycle progression when the cell suffers from DNA damage. We identified the mechanism also affects DNA repairactivities themselves besides its regulate cell cycle progression. We further studied the checkpoint mechanism in dimorphic yeast system. There we found that Chk1 could induce hyphaformation in response to DNA damage, and thus we defined it as the novel cell cycle regulatory function of DNA checkpoint.