Department of Microbiology, University of Georgia, Athens, GA 30602, United States.
DNA Repair (Amst). 2012 Sep 1;11(9):733-40. doi: 10.1016/j.dnarep.2012.06.006. Epub 2012 Jul 8.
Genomic DNA in a bacterial cell is folded into a compact structure called a nucleoid, and nucleoid-associated proteins are responsible for proper assembly of active higher-order genome structures. The human gastric pathogen Helicobacter pylori express a nucleoid-associated protein encoded by the hup gene, which is the homolog to the Escherichia coli histone-like protein HU. An H. pylori hup mutant strain (X47 hup:cat) showed a defect in stationary phase survival. The X47 hup:cat mutant was more sensitive to the DNA damaging agent mitomycin C, and displayed a decreased frequency of DNA recombination, indicating Hup plays a significant role in facilitating DNA recombinational repair. The X47 hup:cat mutant was also sensitive to both oxidative and acid stress, conditions that H. pylori commonly encounters in the host. The hup mutant cells survived significantly (7-fold) less upon exposure to macrophages than the wild type strain. In a mouse infection model, the hup mutant strain displayed a greatly reduced ability to colonize host stomachs. The geometric means of colonization number for the wild type and hup mutant were 6×10(5) and 1.5×10(4)CFU/g stomachs, respectively. Complementation of the hup strain by chromosomal insertion of a functional hup gene restored oxidative stress resistance, DNA transformation frequency, and mouse colonization ability to the wild type level. We directly demonstrated that the purified His-tagged H. pylori Hup protein can protect (in vitro) an H. pylori-derived DNA fragment from oxidative damage.
细菌细胞中的基因组 DNA 折叠成一种称为核小体的紧凑结构，核小体相关蛋白负责正确组装活性的高级基因组结构。人类胃病原体幽门螺杆菌表达由 hup 基因编码的核小体相关蛋白，该蛋白与大肠杆菌组蛋白样蛋白 HU 同源。幽门螺杆菌 hup 突变株（X47 hup:cat）在静止期存活方面存在缺陷。X47 hup:cat 突变体对 DNA 损伤剂丝裂霉素 C 更敏感，并且显示出 DNA 重组频率降低，表明 Hup 在促进 DNA 重组修复中发挥重要作用。X47 hup:cat 突变体也对氧化和酸应激敏感，这是幽门螺杆菌在宿主中常见的条件。与野生型菌株相比，hup 突变细胞在暴露于巨噬细胞时的存活率明显（7 倍）降低。在小鼠感染模型中，hup 突变株定植宿主胃的能力大大降低。野生型和 hup 突变体的定植数量几何平均值分别为 6×10(5)和 1.5×10(4)CFU/g 胃。通过染色体插入功能性 hup 基因对 hup 菌株进行互补，恢复了氧化应激抗性、DNA 转化频率以及小鼠定植能力至野生型水平。我们直接证明了纯化的 His 标记的幽门螺杆菌 Hup 蛋白可以（体外）保护幽门螺杆菌衍生的 DNA 片段免受氧化损伤。
