Naz Saba, Dabral Shruti, Nagarajan Sathya Narayanan, Arora Divya, Singh Lakshya Veer, Kumar Pradeep, Singh Yogendra, Kumar Dhiraj, Varshney Umesh, Nandicoori Vinay Kumar
Signal Transduction Lab, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
Department of Zoology, University of Delhi, Delhi, India.
PLoS Pathog. 2021 Mar 19;17(3):e1009452. doi: 10.1371/journal.ppat.1009452. eCollection 2021 Mar.
Tuberculosis caused by Mycobacterium tuberculosis (Mtb) is a significant public health concern, exacerbated by the emergence of drug-resistant TB. To combat the host's dynamic environment, Mtb encodes multiple DNA repair enzymes that play a critical role in maintaining genomic integrity. Mtb possesses a GC-rich genome, rendering it highly susceptible to cytosine deaminations, resulting in the occurrence of uracils in the DNA. UDGs encoded by ung and udgB initiate the repair; hence we investigated the biological impact of deleting UDGs in the adaptation of pathogen. We generated gene replacement mutants of uracil DNA glycosylases, individually (RvΔung, RvΔudgB) or together (RvΔdKO). The double KO mutant, RvΔdKO exhibited remarkably higher spontaneous mutation rate, in the presence of antibiotics. Interestingly, RvΔdKO showed higher survival rates in guinea pigs and accumulated large number of SNPs as revealed by whole-genome sequence analysis. Competition assays revealed the superior fitness of RvΔdKO over Rv, both in ex vivo and in vivo conditions. We propose that compromised DNA repair results in the accumulation of mutations, and a subset of these drives adaptation in the host. Importantly, this property allowed us to utilize RvΔdKO for the facile identification of drug targets.
由结核分枝杆菌（Mtb）引起的结核病是一个重大的公共卫生问题，耐多药结核病的出现使其更加严重。为了应对宿主的动态环境，Mtb编码多种DNA修复酶，这些酶在维持基因组完整性方面发挥着关键作用。Mtb拥有富含GC的基因组，使其极易受到胞嘧啶脱氨作用的影响，导致DNA中出现尿嘧啶。由ung和udgB编码的UDG启动修复；因此，我们研究了在病原体适应过程中缺失UDG的生物学影响。我们分别（RvΔung、RvΔudgB）或一起（RvΔdKO）产生了尿嘧啶DNA糖基化酶的基因替代突变体。双敲除突变体RvΔdKO在存在抗生素的情况下表现出明显更高的自发突变率。有趣的是，全基因组序列分析显示，RvΔdKO在豚鼠中显示出更高的存活率，并积累了大量单核苷酸多态性（SNP）。竞争试验表明，在体外和体内条件下，RvΔdKO的适应性均优于Rv。我们认为，受损的DNA修复会导致突变的积累，其中一部分突变会促使病原体在宿主体内适应。重要的是，这一特性使我们能够利用RvΔdKO轻松鉴定药物靶点。
