Cao H, Krishnan G, Goumnerov B, Tsongalis J, Tompkins R, Rahme L G
Department of Surgery, Harvard Medical School, Massachusetts General Hospital and Boston Shriners Institute, 50 Blossom Street, Boston, MA 02114, USA.
Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14613-8. doi: 10.1073/pnas.251465298. Epub 2001 Nov 27.
The human opportunistic pathogen Pseudomonas aeruginosa strain PA14 infects both plants and animals. Previously, using plants to screen directly for P. aeruginosa virulence-attenuated mutants, we identified a locus, pho34B12, relevant in mammalian pathogenesis. Here, nonsense point mutations in the two opposing ORFs identified in the pho34B12 locus revealed that one of them, mvfR (multiple virulence factor Regulator), is able to control all of the phenotypes that mutant phoA34B12 displays. Both genetic and biochemical evidence demonstrate that the mvfR gene encodes a LysR-like transcriptional factor that positively regulates the production of elastase, phospholipase, and of the autoinducers, 3oxo-dodecanoyl homoserine lactone (PAI I) and 2-heptyl-3-hydroxy-4-quinolone (PQS), as well as the expression of the phnAB operon, involved in phenazine biosynthesis. We demonstrate that the MvfR protein is membrane-associated and acts as a transcriptional activator until cells reach stationary phase, when a unique negative feedback mechanism is activated to signal the down-regulation of the MvfR protein. This work reveals an unprecedented virulence mechanism of P. aeruginosa and identifies a unique indispensable player in the P. aeruginosa quorum-sensing cascade.
人类机会致病菌铜绿假单胞菌PA14菌株可感染植物和动物。此前，我们利用植物直接筛选铜绿假单胞菌毒力减弱的突变体，鉴定出一个与哺乳动物发病机制相关的基因座pho34B12。在此，pho34B12基因座中鉴定出的两个反向开放阅读框中的无义点突变表明，其中一个基因mvfR（多毒力因子调节因子）能够控制突变体phoA34B12所表现出的所有表型。遗传和生化证据均表明，mvfR基因编码一种类LysR转录因子，该因子正向调节弹性蛋白酶、磷脂酶以及自诱导物3-氧代十二烷酰高丝氨酸内酯（PAI I）和2-庚基-3-羟基-4-喹诺酮（PQS）的产生，以及参与吩嗪生物合成的phnAB操纵子的表达。我们证明，MvfR蛋白与膜相关，在细胞进入稳定期之前作为转录激活因子发挥作用，此时一种独特的负反馈机制被激活，以信号下调MvfR蛋白。这项工作揭示了铜绿假单胞菌前所未有的毒力机制，并在铜绿假单胞菌群体感应级联反应中鉴定出一个独特的不可或缺的参与者。
