CEA, Institut de Radiobiologie Cellulaire et Moléculaire, UMR217 CNRS/CEA, 18 route du Panorama, F-92265 Fontenay aux Roses, France.
J Bacteriol. 2011 Dec;193(23):6490-7. doi: 10.1128/JB.05646-11. Epub 2011 Sep 23.
Helicobacter pylori is a bacterial pathogen colonizing half of the world's human population. It has been implicated in a number of gastric diseases, from asymptomatic gastritis to cancer. It is characterized by an amazing genetic variability that results from high mutation rates and efficient DNA homologous recombination and transformation systems. Here, we report the characterization of H. pylori RecA (HpRecA), a protein shown to be involved in DNA repair, transformation, and mouse colonization. The biochemical characterization of the purified recombinase reveals activities similar to those of Escherichia coli RecA (EcRecA). We show that in H. pylori, HpRecA is present in about 80,000 copies per cell during exponential growth and decreases to about 50,000 copies in stationary phase. The amount of HpRecA remains unchanged after induction of DNA lesions, suggesting that HpRecA is always expressed at a high level in order to repair DNA damage or facilitate recombination. We performed HpRecA localization analysis by adding a Flag tag to the protein, revealing two different patterns of localization. During exponential growth, RecA-Flag presents a diffuse pattern, overlapping with the DAPI (4',6-diamidino-2-phenylindole) staining of DNA, whereas during stationary phase, the protein is present in more defined areas devoid of DAPI staining. These localizations are not affected by inactivation of competence or DNA recombination genes. Neither UV irradiation nor gamma irradiation modified HpRecA localization, suggesting the existence of a constitutive DNA damage adaptation system.
幽门螺杆菌是一种定植于全球半数人口的细菌病原体。它与多种胃部疾病有关，从无症状性胃炎到癌症。其特点是具有惊人的遗传变异性，这是由于高突变率和有效的 DNA 同源重组和转化系统所致。在这里，我们报告了幽门螺杆菌 RecA（HpRecA）的特征，该蛋白被证明参与 DNA 修复、转化和小鼠定植。纯化重组酶的生化特征揭示了与大肠杆菌 RecA（EcRecA）相似的活性。我们表明，在幽门螺杆菌中，RecA 约在指数生长期的每个细胞中存在 80000 个拷贝，在静止期减少到约 50000 个拷贝。在诱导 DNA 损伤后，HpRecA 的数量保持不变，这表明 HpRecA 始终以高水平表达，以修复 DNA 损伤或促进重组。我们通过向该蛋白中添加 Flag 标签来进行 HpRecA 定位分析，揭示了两种不同的定位模式。在指数生长期，RecA-Flag 呈现弥散模式，与 DNA 的 DAPI（4'，6-二脒基-2-苯基吲哚）染色重叠，而在静止期，该蛋白存在于缺乏 DAPI 染色的更明确区域。这些定位不受感受态或 DNA 重组基因失活的影响。紫外线照射或γ射线照射均未改变 HpRecA 的定位，这表明存在一种组成型的 DNA 损伤适应系统。
