The toxin-antitoxin system of Staphylococcus aureus.

TA系统在细菌中很常见。TA系统有8个家族，它们都在类似的原理下运作，具有稳定的毒素和易受应激诱导的蛋白酶的不稳定抗毒素。其中，对MazEF和RelBE体系的研究最为深入。基因组分析显示，在许多革兰氏阳性细菌中存在MazEF和RelBE类似物。初步研究表明，金黄色葡萄球菌中的MazF毒素是一种特异性核糖核酸内切酶，它在V或V可以是a、C或g的VUUV位点切割。我们推测，用小的合成化合物破坏毒素与抗毒素MazE的结合以释放MazF的毒性可能是可行的，从而代表了开发新型抗菌化合物的新途径。我们还研究了MazF对Mrna切割的特异性，发现一些内务和毒力调节Mrna幸免，而其他Mrna如hla、spa和sigB则容易被切割。我们怀疑rna结合蛋白可能保护其中一些mrna。由于我们已经从我们的试点筛选中获得了一些“假定化合物”，我们建议在试验中使用一种新型荧光DNA-RNA杂交底物筛选抗- maze的小合成化合物。为了实现上述目标，我们制定了以下目标：1)鉴定保护选择性mRNA（如选择性内务基因和sarA）免受MazFsa切割的RNA结合蛋白；II)开发一种检测方法来筛选干扰MazEsa与MazFsa功能或结合的小分子。总的来说，这些数据将突出革兰氏+细菌中TA系统的独特性。由于针对耐多药金黄色葡萄球菌的治疗方案有限，我们的筛选试验将为开发针对金黄色葡萄球菌的新型抗菌药物提供针对MazE的初始化合物

TA systems are common in bacteria. There are eight families of TA systems all of which operate under a similar principle, with a stable toxin and a labile antitoxin prone to proteases that are induced upon stress. Among the TA pair, the MazEF and RelBE systems are the best studied. Genomic analysis revealed MazEF and RelBE paralogs in many Gram+ bacteria. Preliminary studies indicated that the MazF toxin in S. aureus is a specific endoribonuclease that cuts at a VUUV’ site where V or V’ can be A, C or G. We speculate that it may be feasible to disrupt the binding of the toxin to the antitoxin MazE with small synthetic compounds to unleash the toxicity of MazF, thus representing a new approach for the development of novel antimicrobial compounds. We also examined the specificity of MazF on Mrna cleavage and found that some housekeeping and virulence regulator mRNAs are spared while others such as hla, spa and sigB are easily cleaved. We suspect RNA-binding protein may protect some of these mRNAs. As we already have a few “putative compounds” from our pilot screen, we propose to screen for small synthetic compounds against anti-MazE, using a novel fluorescent DNA-RNA hybrid substrate in the assay. To satisfy the above goal, we have developed the following aims: I) Identification of RNA binding protein(s) that protects selective mRNA (e.g. selective housekeeping gene and sarA) from MazFsa cleavage; II) developing an assay to screen for small molecule(s) that interferes with function or binding of MazEsa to MazFsa. Collectively, these data will highlight the uniqueness of the TA systems in Gram+ bacteria. As therapy options against multidrug resistant S. aureus are limited, our screening assays will provide the initial compounds against MazE for the development of novel antimicrobial therapy against S. aureus