Regulation/mecA gene expression/clinic S.aureus isolates

描述（由申请人提供）：当今世界范围内医院获得性感染治疗中最严重的挑战之一是对所有β -内酰胺类抗生素耐药的葡萄球菌（称为耐甲氧西林金黄色葡萄球菌；MRSA）的出现和全球传播。葡萄球菌可以通过获得编码β -内酰胺不敏感靶酶青霉素结合蛋白（PBP）2a的基因（mecA）而对β -内酰胺类抗生素产生耐药性。这种酶为细菌提供了交联细胞壁和生长的能力，而细胞通常的交联酶（PBP）被β -内酰胺类抗生素结合并灭活。大多数金黄色葡萄球菌也产生由blaZ编码的/ β -内酰胺酶，该酶可以水解β -内酰胺类抗生素，使其失去活性。mecA和blaZ的转录由相关的双基因操纵子mecRl-mecI和blaRl-blaI调控，它们分别编码信号换能器（R1）和抑制因子(I)。本提案中概述的正在进行的研究是基于先前在实验室菌株中观察到的mecA由MecI和BlaI共同调节。此外，这些观察结果可以扩展到临床相关的分离株，这些分离株可以逃避MecI抑制，以便在/ β -内酰胺压力下存活（36）。本提案的目的是提供证据，证明存在其他基因座参与或需要诱导表达甲氧西林耐药性。这些数据将为MecR1/BlaR1和MecI/BlaI信号转导的分子基础研究提供有价值的结构/功能信息。具体目的是：通过鉴定和表征可能参与诱导mecA/blaZ表达的“mecR2”位点染色体基因，探讨MecR1/BlaR1到MecI/ blal1信号转导的分子基础。为了验证抑制是进化保守的假设，以防止有毒的，受管制的基因产物的过度生产。具体来说，我们将评估在没有β -内酰胺诱导的情况下，诱导过表达MecR1/BlaR1或其相应的突变体/缺失物是否会对细胞产生毒性作用。

DESCRIPTION (provided by applicant): One of the most serious contemporary challenges to the treatment of hospital-acquired infections worldwide is the appearance and global spread of staphylococci resistant to all beta-lactam antibiotics (known as methicillin-resistant S. aureus; MRSA). Staphylococci can become resistant to Beta-lactam antibiotics by acquiring a gene (mecA) that encodes a beta-lactam insensitive target enzyme, penicillin binding protein (PBP)2a. This enzyme affords the bacterium the ability to cross-link cell wall and grow while the cell's usual cross-linking enzymes (PBP's) are bound and inactivated by Beta-lactam antibiotics. Most of S. aureus also produce/beta-lactamase encoded by blaZ, which can hydrolyse Beta-lactam antibiotics rendering them inactive. The transcription of mecA and blaZ is regulated by related divergently transcribed two-gene operons mecRl-mecI and blaRl-blaI, respectively that encode a signal transducer (R1) and a repressor (I). The ongoing studies outlined in this proposal are based on previous observations in laboratory strains that demonstrated the coregulation of mecA by both MecI and BlaI Furthermore, these observations could be extended to clinically relevant isolates which escape MecI repression in order to survive/beta-lactam pressure (36). The goal of this proposal is to provide evidence of the existence of additional loci involved in or required for inducible expression of methicillin resistance. These data will provide valuable structure/function information to complement studies investigating the molecular basis of MecR1/BlaR1 and MecI/BlaI signal transduction. The specific aims are: To Investigate the molecular basis of signal transduction through MecR1/BlaR1 to MecI/Blalby identifying and characterizing "mecR2" loci - chromosomal genes that may contribute to the induction of mecA/blaZ expression. To test the hypothesis that repression is evolutionarily conserved in order to prevent overproduction of a toxic, regulated gene product. Specifically, we will evaluate if the inducible overexpression of either MecR1/BlaR1 or their corresponding mutants/deletants in the absence of Beta-lactam induction results in a toxic effect to the cell.