Identification of novel DNA repair mechanisms in Mycobacterium tuberculosis

描述(由申请人提供)： 项目概述：由结核分枝杆菌引起的结核病感染了约20亿-三分之一-世界人口。这种病原体的成功可以归因于它在宿主体内无限期存活的非凡能力。结核病的治疗需要长期服用三种抗结核药物，以确保彻底根除继续抗拒抗生素的亚群。耐多药和极端耐药结核病的出现是一个巨大的关切，因为它完全消除了所有治疗选择，并推翻了世卫组织为控制这一疾病的传播所作的努力。因此，了解结核分枝杆菌在宿主体内持续存在的机制对于设计一种短期而有效的治疗方法是必不可少的。在感染过程中，结核分枝杆菌受到各种宿主防御机制的挑战，而这些机制是病原体必须克服的。在这些挑战中，感染早期面临的挑战可能是病原体存活以建立成功感染的最关键的挑战。这主要是在肺泡巨噬细胞吞噬细菌时发生的呼吸爆发，并导致活性氧和氮中间体的产生。虽然大多数病原菌是通过感染的巨噬细胞中的这些抗微生物活性来清除的，但结核分枝杆菌已经进化出了颠覆这些挑战以及积极修复造成的损害的机制。DNA中的碱基特别容易受到这些活性氧和氮物种的破坏--因此，细菌必须具有修复损伤的活性机制，以确保病原体的生存。以前的工作表明，分枝杆菌拥有其他细菌所利用的大部分DNA损伤修复系统；此外，它还拥有一些新的基因和途径。考虑到结核分枝杆菌生活在一个富含能够破坏DNA的试剂的环境中，这并不令人惊讶。该项目建议在病原体中寻找新的DNA应激反应途径，这将有助于更好地了解细菌修复其DNA的机制，同时作为治疗靶点非常有吸引力。我们的初步工作已经确定了几个新的基因，这些基因以前没有被证明参与替代宿主耻垢分枝杆菌的DNA损伤修复。虽然从耻垢分枝杆菌中发现的基因为分枝杆菌对抗氧化应激的生存策略提供了宝贵的见解，并有力地支持了关键修复途径仍有待发现的假设，但结核分枝杆菌很可能有更多的基因来维持其生存，因为它必须在细胞内生长。在这份修订后的报告中，我们建议在病原体结核分枝杆菌中鉴定新的DNA损伤修复途径，并研究初步筛选中确定的调节蛋白的参与。) 公共卫生相关性： 项目)叙述))结核病，)caused)by)M.)tuberculosis)infects)nearly)a)third)of)the)world‘s)population)and)kills)about)2)million)people)in)the)world)every)year.)Developing)new)drugs)for)the)disease)requires)a)better)understanding)of)the)mechanisms)the)pathogen)utilizes)to)persist)in)the)challenging)environment.)In)this)project)we)study))新的)机制)由)细菌使用)以反)不断地)攻击)对)DNA)by)the)reactive)oxygen)species)present)in)the)oxidizing)environment)of)macrophages)where)it)resides)for)prolonged)periods)of)time.))

DESCRIPTION (provided by applicant): Project Summary: Tuberculosis (TB), caused by Mycobacterium tuberculosis infects about 2 billion- a third- of the world's population. The success of the pathogen can be attributed to its extraordinary ability to survive indefinitely in the host. The treatment of TB requires a prolonged regimen of three anti-tuberculosis drugs to ensure complete eradication of a sub-population that continues to persist against antibiotics. The emergence of multi-drug resistant and extremely drug resistant TB is a tremendous concern as it completely eliminates all treatment options as well as overturns the effort made by WHO to control the spread of this disease. Therefore an understanding of the mechanism of persistence of M. tuberculosis inside the host is imperative for designing a short and effective treatment against the disease. During the course of infection M. tuberculosis is challenged with a variety of host defense mechanisms which the pathogen has to overcome. Of these, the challenges faced during the early phase of infection are perhaps the most critical for the pathogen to survive so as to establish a successful infection. This primarily constitutes the respiratory burst that occurs upon phagocytosis of the bacteria by alveolar macrophages and results in the generation of reactive oxygen and nitrogen intermediates. Whereas most pathogenic bacteria are cleared by these antimicrobial activities in the infected macrophages, M. tuberculosis has evolved mechanisms to subvert these challenges as well as to actively repair the damage caused. The bases in DNA are particularly susceptible to damage by these reactive oxygen and nitrogen species- the bacteria must therefore possess active mechanisms to repair the damage in order to ensure the survival of the pathogen. Previous work suggests that mycobacteria possess most of the DNA damage repair systems utilized by other bacteria; in addition it has a number of novel genes and pathways as well. This is not very surprising considering that M. tuberculosis resides in an environment rich in agents that can damage DNA. The project here proposes to identify novel DNA stress response pathways in the pathogen which will help in better understanding the mechanisms utilized by the bacteria to repair its DNA and are simultaneously very attractive as therapeutic targets. Our preliminary work has identified several novel genes that have previously not been shown to be involved in DNA damage repair in the surrogate host M. smegmatis. While the genes identified from M. smegmatis provide an invaluable insight into mycobacterial survival strategies against oxidative stress and strongly support the hypothesis that key repair pathways remain to be discovered, it is likely that M. tuberculosis could have additional genes for its survival because of its obligate intracellular growth requirement. In this revised submission we propose to identify novel DNA damage repair pathways in the pathogen, M. tuberculosis as well as study the involvement of regulatory proteins identified in the preliminary screen.) ) PUBLIC HEALTH RELEVANCE: Project)Narrative) ) Tuberculosis,)caused)by)M.)tuberculosis)infects)nearly)a)third)of)the)world's) population)and)kills)about)2)million)people)in)the)world)every)year.)Developing)new) drugs)for)the)disease)requires)a)better)understanding)of)the)mechanisms)the) pathogen)utilizes)to)persist)in)the)challenging)environment.)In)this)project)we)study) the)novel)mechanisms)used)by)bacteria)to)counter)the)constant)assault)on)its)DNA) by)the)reactive)oxygen)species)present)in)the)oxidizing)environment)of)macrophages) where)it)resides)for)prolonged)periods)of)time.))