Zutkis Anastasia A, Anbalagan Srivishnupriya, Chaussee Michael S, Dmitriev Alexander V
Department of Molecular Microbiology, Institute of Experimental Medicine, Saint-Petersburg, Russia.
Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota, United States of America.
PLoS One. 2014 Dec 8;9(12):e114784. doi: 10.1371/journal.pone.0114784. eCollection 2014.
Streptococcus pyogenes adapts to different niches encountered in the human host via the activity of numerous regulatory proteins including the Rgg family of transcriptional regulators. The S. pyogenes chromosome encodes four Rgg paralogues designated Rgg1 (RopB), Rgg2 (MutR), Rgg3, and Rgg4 (ComR). In order to understand the role of the Rgg2 protein in the regulation of metabolic and virulence-associated properties of S. pyogenes, the rgg2 gene was inactivated in the M1 serotype strain SF370. Inactivation of rgg2 increased the growth yield of S. pyogenes in THY broth, increased biofilm formation, and increased production of SIC, which is an important virulence factor that inhibits complement mediated lysis. To identify Rgg2-regulated genes, the transcriptomes of SF370 and the rgg2 mutant strains were compared in the middle-exponential and post-exponential phases of growth. Rgg2 was found to control the expression of dozens of genes primarily in the exponential phase of growth, including genes associated with virulence (sse, scpA, slo, nga, mf-3), DNA transformation, and nucleotide metabolism. Inactivation of rgg2 decreased the ability of S. pyogenes to adhere to epithelial cells. In addition, the mutant strain was more sensitive to killing when incubated with human blood and avirulent in a murine bacteremia model. Finally, inoculation of mice with the avirulent rgg2 mutant of S. pyogenes SF370 conferred complete protection to mice subsequently challenged with the wild-type strain. Restoration of an intact rgg2 gene in mutant strain restored the wild-type phenotypes. Overall, the results demonstrate that Rgg2 is an important regulatory protein in S. pyogenes involved in controlling genes associated with both metabolism and virulence.
化脓性链球菌通过众多调控蛋白的活性来适应人类宿主中遇到的不同生态位，这些调控蛋白包括转录调控因子Rgg家族。化脓性链球菌染色体编码四种Rgg旁系同源物，分别命名为Rgg1（RopB）、Rgg2（MutR）、Rgg3和Rgg4（ComR）。为了了解Rgg2蛋白在化脓性链球菌代谢和毒力相关特性调控中的作用，rgg2基因在M1血清型菌株SF370中被灭活。rgg2的灭活提高了化脓性链球菌在THY肉汤中的生长产量，增加了生物膜形成，并增加了SIC的产生，SIC是一种重要的毒力因子，可抑制补体介导的裂解。为了鉴定受Rgg2调控的基因，在生长的指数中期和指数后期比较了SF370和rgg2突变株的转录组。发现Rgg2主要在生长的指数期控制数十个基因的表达，包括与毒力相关的基因（sse、scpA、slo、nga、mf-3）、DNA转化和核苷酸代谢。rgg2的灭活降低了化脓性链球菌黏附上皮细胞的能力。此外，突变株在与人血孵育时对杀伤更敏感，并且在小鼠菌血症模型中无毒力。最后，用化脓性链球菌SF370的无毒力rgg2突变株接种小鼠，可使随后受到野生型菌株攻击的小鼠获得完全保护。在突变株中恢复完整的rgg2基因可恢复野生型表型。总体而言，结果表明Rgg2是化脓性链球菌中一种重要的调控蛋白，参与控制与代谢和毒力相关的基因。
