EXPRESSION AND PHASE VARIATION OF GONOCOCCAL OPA GENES

淋球菌 OPA 基因的表达和相变

• 批准号: 3768852
• 负责人: R J BELLAND
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3768852
• 关键词: Escherichia coli; Neisseria gonorrhoeae; bacterial DNA; bacterial genetics; bacterial proteins; cell adhesion; chimeric proteins; epithelium; gene expression; genetic promoter element; genetic regulation; genetic strain; genetic transcription; host organism interaction; human tissue; membrane proteins; neutrophil; nucleic acid repetitive sequence; structural genes

Major constituents of the bacterial outer-membrane of Neisseria gonorrhoeae, including the lipooligosaccharide (LOS), pilin, and Opa proteins have been demonstrated to change expression states and antigenic nature during controlled challenge studies in human volunteers. Opa genes exhibit high frequency phase variation (on-off expression) due to changes at the DNA level resulting in translational frame-shifting. Phase variation occurs when a gene undergoes an insertion or deletion of one or more pentameric repeat units (i.e. [CTTCT], referred to as a coding repeat or 'CR') which encode the central portion of the signal-peptide. These changes are independent of homologous recombination pathways and are therefore referred to as 'non-homologous' or 'illegitimate' recombinational (IR) events. Factors influencing IR in a general manner have been determined in E. coli using opa::phoA fusions on low copy number vectors. Genes encoding the homologs of the cellular enzymes found to influence phase variation have been identified in N. gonorrhoeae, and their role in opa phase variation is presently being evaluated by deletion mutagenesis. Transcriptional influences on opa phase variation are being investigated by determining the efficiency of transcriptional initiation by each of the three different promoter types found in the opa genes of strain MS11. The role of structural elements within the repetitive region of opa genes has been extended by the demonstration that intermolecular DNA triplexes form with the addition of the pyrimidine sense repeat oligonucleotide. Interactions of Opa+ N. gonorrhoeae and E. coli with PMNs and epithelial cells have shown that expression of specific proteins leads to adherence to both of these cell types. Chimeric versions of Opa fusion proteins do not clearly identify regions of the protein which impart these biological activities. Recombinant Opa fusions have been shown to destabilize the outer-membrane of E. coli K12 strains. Strains producing E. coli B type LPS and hybrids of K12/B type LPS (e.g. HB101) are better suited to biological assays with Opa fusion proteins. The interaction of Opa+ N. gonorrhoeae with normal human sera has been partially characterized. While Opa expression does not appear to directly influence survival in human serum, the addition of human urine does appear to impart an Opa- specific protective effect (which is most pronounced in Opa+, Pili+ bacteria).

奈瑟氏菌属细菌外膜的主要成分 淋病，包括脂寡糖（LOS）、菌毛蛋白和Opa 已经证明蛋白质改变表达状态和抗原性， 在人类志愿者中进行的对照激发研究中。 Opa基因 由于变化而表现出高频相位变化（开-关表达式 在DNA水平导致翻译移码。 相 当一个基因发生一个或多个碱基的插入或缺失时， 更多的五聚体重复单元（即[CTTCT]，称为编码重复 或“CR”），其编码信号肽的中心部分。这些 变化独立于同源重组途径， 因此被称为“非同源”或“非法” 重组（IR）事件。 影响IR的一般因素已在E.杆菌 在低拷贝数载体上使用opa：：phoA融合。 基因编码的 已发现影响相位变化的细胞酶的同源物， 在N.淋病及其在OPA时相变化中的作用 目前正在通过缺失突变进行评估。 转录 对OPA相位变化的影响通过确定 这三种基因中的每一种的转录起始效率 在菌株MS 11的opa基因中发现的不同启动子类型。的作用 在opa基因重复区域内的结构元件已经被 通过证明分子间DNA三链体与 嘧啶有义重复寡核苷酸的添加。 Opa+ N的相互作用淋病和E.大肠杆菌与中性粒细胞和上皮细胞 细胞已经表明，特定蛋白质的表达导致粘附， 这两种细胞类型。 Opa融合蛋白的嵌合形式 没有清楚地识别赋予这些生物学特性的蛋白质区域， 活动 重组Opa融合物已显示使细胞不稳定， E. coli K12菌株。产E.大肠杆菌B型 LPS和K12/B型LPS的杂交体（例如HB 101）更适合于 使用Opa融合蛋白的生物测定。 Opa+ N. 淋病与正常人血清的关系已被部分表征。 虽然Opa表达似乎并不直接影响存活率， 人血清，加入人尿似乎确实赋予了Opa- 特异性保护作用（在Opa+、皮利+中最明显 细菌）。