title: Use of a Phosphorylation Site Mutant To Identify Distinct Modes of Gene Repression by the Control of Virulence Regulator (CovR) in Streptococcus pyogenes.
abstract: Control of the virulence regulator/sensor kinase (CovRS) two-component system (TCS) serves as a model for investigating the impact of signaling pathways on the pathogenesis of Gram-positive bacteria. However, the molecular mechanisms by which CovR, an OmpR/PhoB family response regulator, controls virulence gene expression are poorly defined, partly due to the labile nature of its aspartate phosphorylation site. To better understand the regulatory effect of phosphorylated CovR, we generated the phosphorylation site mutant strain 10870-CovR-D53E, which we predicted to have a constitutive CovR phosphorylation phenotype. Interestingly, this strain showed CovR activity only for a subset of the CovR regulon, which allowed for classification of CovR-influenced genes into D53E-regulated and D53E-nonregulated groups. Inspection of the promoter sequences of genes belonging to each group revealed distinct promoter architectures with respect to the location and number of putative CovR-binding sites. Electrophoretic mobility shift analysis demonstrated that recombinant CovR-D53E protein retains its ability to bind promoter DNA from both CovR-D53E-regulated and -nonregulated groups, implying that factors other than mere DNA binding are crucial for gene regulation. In fact, we found that CovR-D53E is incapable of dimerization, a process thought to be critical to OmpR/PhoB family regulator function. Thus, our global analysis of CovR-D53E indicates dimerization-dependent and dimerization-independent modes of CovR-mediated repression, thereby establishing distinct mechanisms by which this critical regulator coordinates virulence gene expression.IMPORTANCEStreptococcus pyogenescauses a wide variety of diseases, ranging from superficial skin and throat infections to life-threatening invasive infections. To establish these various disease manifestations,Streptococcus pyogenesrequires tightly coordinated production of its virulence factor repertoire. Here, the response regulator CovR plays a crucial role. As an OmpR/PhoB family member, CovR is activated by phosphorylation on a conserved aspartate residue, leading to protein dimerization and subsequent binding to operator sites. Our transcriptome analysis using the monomeric phosphorylation mimic mutant CovR-D53E broadens this general notion by revealing dimerization-independent repression of a subset of CovR-regulated genes. Combined with promoter analyses, these data suggest distinct mechanisms of CovR transcriptional control, which allow for differential expression of virulence genes in response to environmental cues.
authors.affiliation: Department of Infectious Diseases, Infection Control and Employee Health, MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Horstmann
authors.affiliation: Department of Infectious Diseases, Infection Control and Employee Health, MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Pranoti
authors.initials: P
authors.lastname: Sahasrabhojane
authors.affiliation: Department of Bioinformatics and Computational Biology, MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Yao
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Su
authors.affiliation: Department of Infectious Diseases, Infection Control and Employee Health, MD Anderson Cancer Center, Houston, Texas, USA sshelburne@manderson.org.|Department of Genomic Medicine, MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Shelburne
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D013297:Streptococcus pyogenes / Q000235:genetics*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C432143:CsrR protein, Streptococcus pyogenes; D004269:DNA, Bacterial; D050505:Mutant Proteins; D012097:Repressor Proteins
keywords: Streptococcus pyogenes; dimerization; pathogenesis; regulation of gene expression; transcriptional regulation; two-component regulatory systems; virulence regulation