Single-molecule study on histone-like nucleoid-structuring protein (H-NS) paralogue in Pseudomonas aeruginosa: MvaU bears DNA organization mode similarities to MvaT.

Pseudomonas aeruginosa contains two distinct members of H-NS family of nucleoid-structuring proteins: MvaT and MvaU. Together, these proteins bind to the same regions of the chromosome and function coordinately in the regulation of hundreds of genes. Due to their structural similarity, they can associate to form heteromeric complexes. These findings left us wondering whether they bear similar DNA binding properties that underlie their gene-silencing functions. Using single-molecule stretching and imaging experiments, we found striking similarities in the DNA organization modes of MvaU compared to the previously studied MvaT. MvaU can form protective nucleoprotein filaments that are insensitive to environmental factors, consistent with its role as a repressor of gene expression. Similar to MvaT, MvaU filament can mediate DNA bridging while excessive MvaU can cause DNA aggregation. The almost identical DNA organization modes of MvaU and MvaT explain their functional redundancy, and raise an interesting question regarding the evolutionary benefits of having multiple H-NS paralogues in the Pseudomonas genus.

铜绿假单胞菌含有类核结构蛋白H - NS家族的两个不同成员：MvaT和MvaU。这些蛋白质共同结合到染色体的相同区域，并在数百个基因的调控中协同发挥作用。由于它们结构相似，它们可以结合形成异聚复合物。这些发现让我们想知道它们是否具有相似的DNA结合特性，而这种特性是它们基因沉默功能的基础。通过单分子拉伸和成像实验，我们发现与之前研究的MvaT相比，MvaU的DNA组织模式具有惊人的相似性。MvaU可以形成对环境因素不敏感的保护性核蛋白丝，这与其作为基因表达抑制因子的作用一致。与MvaT类似，MvaU丝可以介导DNA桥接，而过量的MvaU会导致DNA聚集。MvaU和MvaT几乎相同的DNA组织模式解释了它们的功能冗余，并提出了一个有趣的问题，即铜绿假单胞菌属中存在多个H - NS旁系同源物的进化优势。