GENETIC RECOMBINATION IN MYCOPLASMAS

支原体中的基因重组

• 批准号: 6490079
• 负责人: KEVIN F DYBVIG
• 金额: $ 26.55万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6490079
• 关键词: Mycoplasma; bacteria infection mechanism; bacterial DNA; bacterial antigens; bacterial cytopathogenic effect; bacterial genetics; bacterial proteins; chromosome inversion; gene expression; gene mutation; gene rearrangement; genetic library; genetic polymorphism; genetic recombination; laboratory mouse; laboratory rat; molecular pathology; mutant; nucleic acid sequence; phenotype; polymerase chain reaction; protein structure function; recombinase; transposon /insertion element; virulence

DESCRIPTION (ADPATED FROM APPLICANT'S ABSTRACT): Mycoplasmas are, widely distributed in nature and commonly produce disease in plants, insects, and animals, including man. Although the economic impact of these diseases is great, little information is available concerning mechanisms of pathogenesis and effective methods of control are unavailable. The surface properties of numerous mycoplasma species vary at high rate, about 10-3 per cell per generation. In the murine pathogen Mycoplasma pulmonis, high-frequency phenotypic variations involving changes in variable surface antigens (VI antigens) affect colony morphology, the susceptibility of the organism to mycoplasma viruses, and the adsorption of mycoplasmas to red blood cells. Most of the high-frequency phenotypic variations in M. pulmonis result from site-specific DNA inversions occurring in the hsd loci (encoding complex, phase-variable restriction and modification systems) and the vsa locus (encoding the phase-variable V-1 surface proteins). The finding of phase-variable restriction and modification systems is novel and challenges the notion that the function of restriction systems in bacteria is limited to the protection of cells from invasion by foreign DNA (phage infection). This challenge takes on added dimension by the observation that DNA inversions within vsa and within hsd apparently occur in concert. The long-range goals are to understand the molecular basis of mycoplasmal chromosomal and phenotypic variation and the role these variations have in disease pathogenesis. Completion of these goals is essential for the development of control measures for mycoplasmal diseases and into pathogenic mechanisms of bacterial diseases. The genome of M. pulmonis will have been fully sequenced by the end of 1999. This application proposes to capitalize on the forthcoming sequence information through the construction of a transposon library of M. pulmonis mutants. In aim 1, the chromosomal site of transposon insertion will be determined for each mutant to precisely identify the mutated gene. In aim 2, mutants with defects in putative DNA recombinases and V-I protein production will be examined to study the mechanisms of gene rearrangements and phenotypic switching.

描述（改编自申请人的摘要）：支原体广泛存在于 分布于自然界，通常在植物、昆虫和植物中引起疾病 动物，包括人。尽管这些疾病的经济影响 关于发病机制的信息很少 并且缺乏有效的控制方法。的表面特性 许多支原体种类变化率很高，每个细胞大约有 10-3 个 一代。在鼠类病原体肺支原体中，高频 表型变异涉及可变表面抗原的变化（VI 抗原）影响集落形态，生物体对 支原体病毒，以及支原体对红细胞的吸附。最多 M. pulmonis 的高频表型变异源于 位点特异性 DNA 倒位发生在 hsd 位点（编码复合体， 相变限制和修饰系统）和 vsa 基因座 （编码相变 V-1 表面蛋白）。的发现 相变限制和修改系统是新颖的，挑战了 认为细菌限制系统的功能仅限于 保护细胞免受外来 DNA 的入侵（噬菌体感染）。这 通过观察 DNA 倒置，挑战变得更加维度 在 vsa 内和在 hsd 内显然是一致发生的。长期目标是 了解支原体染色体和表型的分子基础 变异以及这些变异在疾病发病机制中的作用。 完成这些目标对于制定控制措施至关重要 用于支原体疾病和细菌性疾病的致病机制。 肺支原体的基因组将于 1999 年底完成完整测序。 该申请建议利用即将发布的序列信息 通过构建肺支原体突变体的转座子文库。瞄准目标 1、转座子插入的染色体位点将被确定 突变体以精确识别突变基因。在目标 2 中，有缺陷的突变体 将检查推定的 DNA 重组酶和 V-I 蛋白的产生 研究基因重排和表型转换的机制。