Molecular mechanism of microbial DNA partitioning : structure and function

细菌细胞中的质粒具有以着丝粒为基础的分离系统，以确保其忠实地传递到子细胞，并被作为染色体分配机制的模型系统进行研究。我们研究了这些质粒分割机制背后的一般机制，发现SOPA和ParA蛋白并不直接拉动推送质粒DNA，而是通过使蛋白质浓度的梯度来引导质粒走向正确的方向。值得注意的是，SOPA或ParA蛋白的梯度是从细胞内的聚合中心形成的(SOPA在细胞内形成细丝，ParA位于细胞核上)。我们也一直在研究细菌染色体的传播机制。作为染色体传递引导蛋白，我们鉴定了新的MIGP因子和电子传递链NuoG复合体I的一个组分。两者都是膜结合蛋白，我们认为DNA传递机制可能与膜的定位有关。真核细胞中的DNA检查点机制在细胞遭受DNA损伤时阻止了细胞周期的进展。我们发现，该机制除了调节细胞周期进程外，还影响DNA修复活性本身。我们进一步研究了二相型酵母系统中的检查点机制。在那里，我们发现Chk1可以诱导菌丝形成以响应DNA损伤，因此我们将其定义为DNA检查点的新的细胞周期调节功能。

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.