结核分枝杆菌毒素-抗毒素伴侣系统基因多态性初步研究

目的 研究结核分枝杆菌毒素-抗毒素伴侣(TAC)系统中higA、higB和Rv1957在结核分枝杆菌及其不同亚型菌株中的基因多态性,并探讨其生理意义。方法 选取183株结核分枝杆菌临床菌株,经间隔区寡核苷酸方法进行基因分型,同时分析TAC系统基因higA、higB和Rv1957的PCR扩增及序列,利用I-Mutant 2.0软件预测非同义突变对蛋白结构和功能的影响。结果 183株中138株(75.41%)属北京家族,45株(24.59%)属非北京家族。共149株菌(81.42%)的TAC系统发生突变,包括2种同义突变和6种非同义突变:同义突变发生于higA基因,仅见于北京家族菌株;3个基因均可见非同义突变,其中2种非同义突变仅见于非北京家族菌株,其余4种突变仅见于北京家族菌株。6种非同义突变中有4种突变可能影响蛋白的功能。位于higA基因的CAC121CAT突变位点在单耐链霉素和单耐利福平菌株中的突变频率高于敏感株,且差异有统计学意义(P<0.05)。结论 结核分枝杆菌中的TAC系统具有一定的基因多态性,其中北京家族呈现更高的多态性水平,可能更有利于适应不同的宿主环境。

Polymorphisms of toxin-antitoxin-chaperone system of Mycobacterium tuberculosis complex in China

Objective To investigate the single nucleotide polymorphism (SNP) of toxin- antitoxin-chaperone (TAC) system of Mycobacterium(M.) tuberculosis with different genotypes and its biological significance. Methods A total of 183 clinical M. tuberculosis isolates were collected for spoligotyping. The sequences of higA, higB and Rv1957 were obtained by using PCR and DNA sequencing. The sequences were compared for possible mutations. Functional consequences of nonsynonymous SNPs were predicted by using I-Mutant 2.0 servers. Results Among the 183 M. tuberculosis isolates, 138(75.41%) belonged to the Beijing family, while 45(24.59%) belonged to the non-Beijing family. A total of 149(81.42%) isolates showed polymorphisms in the TAC system. We discovered 6 nonsynonymous SNPs and 2 synonymous SNPs. All the synonymous mutations occurred in higA gene, while nonsynonymous SNPs were found in the higA, higB and Rv1957 genes either. All the synonymous mutations and 4 nonsynonymous SNPs were restricted to the Beijing family strains and only 2 nonsynonymous SNPs were observed in the non-Beijing family strains. Of the 6 nonsynonymous SNPs studied, 4 were predicted to have ability to affect the stability of respective protein. Conclusion The SNPs in the coding sequences of TAC system in clinical isolates can be relatively high and the Beijing family strains are with higher polymorphism, which might benefit to adapt to different host environment.