Alternative ribosomes and antibiotic tolerance in mycobacteria.

项目摘要 进化上遥远的细菌物种通过重新编程它们对锌饥饿的反应。 核糖体组装，其中具有锌结合基序CXXC的组成性核糖体蛋白 （C+）通过转录脱锌被替代的无锌对应物（C-）取代。 抑制机制涉及锌吸收调节剂，BMPB。替代核糖体 与C-核糖体蛋白质组装，减少细胞生长对锌的需求， 锌限制条件。结核分枝杆菌（Mtb），结核病的病原体 (TB)具有四个C+/C-核糖体蛋白对。这对编码C蛋白的所有四个基因都是 组织在操纵子中，并通过一个可阻遏的启动子共表达。共 表达意味着所有四种C+蛋白同时被C-旁系同源物取代， 关于取代对核糖体对抗生素反应的影响的问题。我们有 发现结核分枝杆菌和耻垢分枝杆菌中的替代性C-核糖体不仅 减少细胞生长的锌需求，而且还赋予临床相关的耐受性， 抗结核核糖体抗生素我们进一步观察到结核分枝杆菌表达更多的替代核糖体， 在慢性感染期比在急性感染早期。因此，我们假设， 替代性核糖体是导致临床治疗无效的主要原因。 建立了抗结核的核糖体抗生素。为了促进改进分枝杆菌的靶向， 核糖体，我们建议：a）阐明差异反应的机制基础， 抗生素的组成型（C+）和替代型（C-）核糖体（目的1），B）鉴定策略， 靶向选择性（C-）核糖体（aim 2）和c）确定选择性核糖体在 Mtb的发病机制（目的3）。这些研究最终将导致针对这两个目标的新战略 在分枝杆菌中的组成型和替代型核糖体，从而允许有效清除 分枝杆菌感染

Project Summary Evolutionarily distant bacterial species respond to zinc starvation by reprogramming their ribosome assembly, in which the constitutive ribosomal proteins with zinc-binding motifs CXXC (C+) are substituted with alternative zinc-free counterparts (C-) through a transcriptional de- repression mechanism involving the zinc uptake regulator, ZurB. The alternative ribosomes assembled with C- ribosomal proteins reduce the zinc requirement for cellular growth under zinc-limiting conditions. Mycobacterium tuberculosis (Mtb), the etiological agent for tuberculosis (TB), has four C+/C- ribosomal protein pairs. All four genes encoding C- proteins of the pair are organized in an operon and are co-expressed through a ZurB-repressible promoter. Co- expression implies simultaneous substitution of all four C+ proteins by C- paralogs, raising questions about the influence of the substitutions on ribosomal response to antibiotics. We have found that the alternative C- ribosomes in both Mtb and Mycobacterium smegmatis not only reduce the zinc requirement for cellular growth, but also confer tolerance to clinically relevant anti-TB ribosomal antibiotics. We further observed that Mtb express more alternative ribosomes during chronic infection than in early acute phase. We thus hypothesize that expression of alternative ribosomes are the primary reasons underlying the inefficacies of the clinically established ribosomal antibiotics against TB. To facilitate improved targeting of mycobacterial ribosomes we propose to: a) elucidate the mechanistic basis of differential responses of constitutive (C+) and alternative (C-) ribosomes to antibiotics (aim 1), b) identify strategies to target alternative (C-) ribosomes (aim 2) and c) determine the role of alternative ribosomes in pathogenesis of Mtb (aim 3). These studies will ultimately lead to new strategies to target both constitutive and alternative ribosomes in mycobacteria, and thus allow effective clearance of mycobacterial infections.