Macrolide antibiotics bind to 23S rRNA within the peptide exit tunnel of the ribosome, causing the translating ribosome to stall when an appropriately positioned macrolide arrest motif is encountered in the nascent polypeptide. Tylosin is a macrolide antibiotic produced by Streptomyces fradiae Resistance to tylosin in S. fradiae is conferred by methylation of 23S rRNA by TlrD and RlmAII Here, we demonstrate that yxjB encodes RlmAII in Bacillus subtilis and that YxjB-specific methylation of 23S rRNA in the peptide exit tunnel confers tylosin resistance. Growth in the presence of subinhibitory concentrations of tylosin results in increased rRNA methylation and increased resistance. In the absence of tylosin, yxjB expression is repressed by transcription attenuation and translation attenuation mechanisms. Tylosin-dependent induction of yxjB expression relieves these two repression mechanisms. Induction requires tylosin-dependent ribosome stalling at an RYR arrest motif at the C terminus of a leader peptide encoded upstream of yxjB Furthermore, NusG-dependent RNA polymerase pausing between the leader peptide and yxjB coding sequences is essential for tylosin-dependent induction. Pausing synchronizes the position of RNA polymerase with ribosome position such that the stalled ribosome prevents transcription termination and formation of an RNA structure that sequesters the yxjB ribosome binding site. On the basis of our results, we are renaming yxjB as tlrB IMPORTANCE Antibiotic resistance is a growing health concern. Resistance mechanisms have evolved that provide bacteria with a growth advantage in their natural habitat such as the soil. We determined that B. subtilis, a Gram-positive soil organism, has a mechanism of resistance to tylosin, a macrolide antibiotic commonly used in the meat industry. Tylosin induces expression of yxjB, which encodes an enzyme that methylates 23S rRNA. YxjB-dependent methylation of 23S rRNA confers tylosin resistance. NusG-dependent RNA polymerase pausing and tylosin-dependent ribosome stalling induce yxjB expression, and hence tylosin resistance, by preventing transcription termination upstream of the yxjB coding sequence and by preventing repression of yxjB translation.

中文翻译：

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通过诱导枯草芽孢杆菌中的23S rRNA甲基化，泰乐菌素耐药性需要依赖NusG依赖的RNA聚合酶暂停和依赖泰乐菌素的核糖体失速。

大环内酯类抗生素与核糖体的肽出口通道内的23S rRNA结合，当在新生多肽中遇到适当定位的大环内酯类逮捕基序时，导致翻译核糖体失速。泰乐菌素是由链霉菌产生的大环内酯类抗生素。通过TlrD和RlmAII对23S rRNA的甲基化作用赋予了对链霉菌中泰乐菌素的抗性。在这里，我们证明yxjB编码枯草芽孢杆菌中的RlmAII，并且该肽中23S rRNA的YxjB特异性甲基化出口隧道赋予泰乐菌素抗性。在亚抑制浓度的泰乐菌素存在下生长会导致rRNA甲基化增加和耐药性增加。在没有泰乐菌素的情况下，yxjB的表达被转录衰减和翻译衰减机制所抑制。yxjB表达的泰洛菌素依赖性诱导减轻了这两种阻抑机制。诱导需要在yxjB上游编码的前导肽的C末端的RYR阻滞基序处酪蛋白素依赖性核糖体失速。此外，在前导肽和yxjB编码序列之间暂停的NusG依赖性RNA聚合酶对于泰乐菌素依赖性诱导至关重要。暂停可使RNA聚合酶的位置与核糖体位置同步，从而使停滞的核糖体阻止转录终止和形成隔离yxjB核糖体结合位点的RNA结构的形成。根据我们的结果，我们将yxjB重命名为tlrB重要抗生素耐药性日益引起人们的健康关注。已经发展了抗性机制，为细菌在其自然栖息地（例如土壤）中提供了生长优势。我们确定枯草芽孢杆菌（一种革兰氏阳性土壤生物体）具有对泰乐菌素（一种在肉类行业中常用的大环内酯类抗生素）的抗性机制。泰乐菌素诱导yxjB的表达，后者编码一种甲基化23S rRNA的酶。YxjB依赖的23S rRNA甲基化赋予泰乐菌素抗性。通过阻止yxjB编码序列上游的转录终止并防止yxjB翻译的抑制，NusG依赖的RNA聚合酶暂停和泰乐菌素依赖的核糖体失速诱导yxjB表达，进而引起泰乐菌素抗性。YxjB依赖的23S rRNA甲基化赋予泰乐菌素抗性。通过阻止yxjB编码序列上游的转录终止并防止yxjB翻译的抑制，NusG依赖的RNA聚合酶暂停和泰乐菌素依赖的核糖体失速诱导yxjB表达，进而引起泰乐菌素抗性。YxjB依赖的23S rRNA甲基化赋予泰乐菌素抗性。通过阻止yxjB编码序列上游的转录终止并防止yxjB翻译的抑制，NusG依赖的RNA聚合酶暂停和泰乐菌素依赖的核糖体失速诱导yxjB表达，进而引起泰乐菌素抗性。