Epigenetic Control of Bacterial Virulence

细菌毒力的表观遗传控制

• 批准号: 6894282
• 负责人: MICHAEL J MAHAN
• 金额: $ 29.02万
• 依托单位: UNIVERSITY OF CALIFORNIA SANTA BARBARA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6894282
• 关键词: DNA methylation; Salmonella infections; Salmonella typhimurium; bacteria infection mechanism; bacterial genetics; gene expression; genetic regulation; host organism interaction; laboratory mouse; methyltransferase; nucleic acid sequence; operon; pilus; plasmids; polymerase chain reaction; virulence

DESCRIPTION (provided by applicant): Epigenetic control of gene expression is employed in animals and plants to enable genetically identical cells to pursue different fates, and such cell differentiation is central to their development. Epigenetic modification and information transfer may also be employed during the bacterial infection cycle so as to change the expression of virulence functions temporally and spatially within the host. These alterations in gene expression may accompany bacterial dissemination among host sites, and in response to host inflammation, tissue breakdown, and immune reactions. In Aim 1, we propose to test the hypothesis that a methylation-based epigenetic system controls Salmonella pathogenesis. Our proposal is based on altering the expression of the bacterial methyltransferase, termed DNA adenine methylase (Dam), which is involved in the formation of DNA methylation patterns and is known to be required for virulence in a number of pathogens. We propose to determine whether transient overexpression of Dam activity in S. typhimurium leads to the establishment of a lineage of genotypically wild-type, epigenetically modified cells that exhibit altered DNA methylation patterns and altered virulence states that persist for a number of cell generations. If so, the present state of virulence gene expression in a given bacterial cell may be dependent on its past history (i.e., cellular memory), similar to that observed in cell-differentiation and developmental programs in higher organisms. In Aim 2, we propose to specify the mechanism by which cellular memory control occurs at the level of a single gene using the S. typhimurium pef operon as a model system. Plasmid encoded fimbriae (Pef) expressed by S. typhimurium mediate adherence to intestinal epithelium and are required for virulence. The pef operon is under methylation-dependent transcriptional regulation similar to the well characterized E. coli pap operon, which encodes important virulence determinants in urinary tract infections. We propose to test whether Dam overproduction-mediated defects in pef expression are a direct consequence of altered DNA methylation patterns that map to specific upstream pef Dam-target sites (GATC sequences). We further propose to determine whether transient exposure to dam overexpression leads to persistent changes in Pef synthesis and whether such changes are heritably maintained via altered DNA methylation patterns at upstream Per GATC sites. The finding of a methylation-based memory system in bacteria would provide profound insights into the fundamental molecular mechanism(s) underlying control of virulence gene expression and the resultant changes in pathogen behavior that are critical to infection. Such information is vital toward developing novel antimicrobials and vaccines against biowarfare agents and emerging infectious diseases that currently threaten public health worldwide.

描述（由申请人提供）：在动物和植物中采用基因表达的表观遗传控制，以使遗传上相同的细胞能够追求不同的命运，并且这种细胞分化对其发育至关重要。表观遗传修饰和信息传递也可以在细菌感染周期中使用，以便在时间和空间上改变宿主内毒力功能的表达。这些基因表达的改变可能伴随着宿主部位之间的细菌传播，以及对宿主炎症，组织分解和免疫反应的反应。在目的1中，我们提出了一个基于甲基化的表观遗传系统控制沙门氏菌发病机制的假设进行测试。我们的建议是基于改变细菌甲基转移酶的表达，称为DNA腺嘌呤甲基化酶（Dam），它参与DNA甲基化模式的形成，并且已知是许多病原体中毒力所需的。我们建议确定是否在S.鼠伤寒沙门氏菌导致建立基因型野生型、表观遗传修饰的细胞谱系，其表现出改变的DNA甲基化模式和改变的毒力状态，并持续多个细胞代。如果是这样，则给定细菌细胞中毒力基因表达的当前状态可能取决于其过去的历史（即，细胞记忆），类似于在高等生物的细胞分化和发育程序中观察到的。在目标2中，我们提出了具体的机制，细胞记忆控制发生在一个单一的基因水平上使用的S。鼠伤寒杆菌PEF操纵子作为模型系统。质粒编码的菌毛（Pef）由S.鼠伤寒沙门氏菌介导对肠上皮的粘附，并且是毒力所必需的。pef操纵子是在甲基化依赖的转录调控下，类似于已充分表征的E。大肠杆菌pap操纵子，编码泌尿道感染中重要的毒力决定因子。我们建议测试是否大坝生产过剩介导的缺陷，在pef表达的DNA甲基化模式，映射到特定的上游pef大坝目标位点（GATC序列）改变的直接后果。我们进一步建议，以确定是否短暂暴露于dam过表达导致Pef合成的持续变化，以及这种变化是否通过改变上游Per GATC位点的DNA甲基化模式遗传维持。细菌中基于甲基化的记忆系统的发现将为毒力基因表达控制的基本分子机制以及由此产生的对感染至关重要的病原体行为变化提供深刻的见解。这些信息对于开发针对生物战剂和目前威胁全球公共卫生的新兴传染病的新型抗菌剂和疫苗至关重要。

项目成果

Cross-protective immunity in calves conferred by a DNA adenine methylase deficient Salmonellaenterica serovar Typhimurium vaccine.

DNA 腺嘌呤甲基化酶缺陷的肠沙门氏菌血清型鼠伤寒疫苗赋予犊牛交叉保护性免疫力。

• DOI: 10.1016/j.vaccine.2005.09.022
• 发表时间: 2006
• 期刊: Vaccine
• 影响因子: 5.5
• 作者: Mohler,VirginiaL;Heithoff,DougM;Mahan,MichaelJ;Walker,KeithH;Hornitzky,MichaelA;McConnell,CraigS;Shum,LucyWC;House,JohnK
• 通讯作者: House,JohnK

In vivo-selected mutations in methyl-directed mismatch repair suppress the virulence attenuation of Salmonella dam mutant strains following intraperitoneal, but not oral, infection of naïve mice.

甲基定向错配修复中的体内选择突变抑制了幼鼠腹膜内而非口腔感染后沙门氏菌坝突变株的毒力减弱。

• DOI: 10.1128/jb.00299-07
• 发表时间: 2007
• 期刊: Journal of bacteriology
• 影响因子: 3.2
• 作者: Heithoff,DouglasM;Badie,Golnaz;Julio,StevenM;Enioutina,ElenaY;Daynes,RaymondA;Sinsheimer,RobertL;Mahan,MichaelJ
• 通讯作者: Mahan,MichaelJ