Polymorphisms in Regulator of Cov Contribute to the Molecular Pathogenesis of Serotype M28 Group A Streptococcus

Abstract

Two-component systems (TCSs) are signal transduction proteins that enable bacteria to respond to external stimuli by altering the global transcriptome. Accessory proteins interact with TCSs to fine-tune their activity. In group A Streptococcus (GAS), regulator of Cov (RocA) is an accessory protein that functions with the control of virulence regulator/sensor TCS, which regulates approximately 15% of the GAS transcriptome. Whole-genome sequencing analysis of serotype M28 GAS strains collected from invasive infections in humans identified a higher number of missense (amino acidealtering) and nonsense (protein-truncating) polymorphisms in rocA than expected. We hypothesized that polymorphisms in RocA alter the global transcriptome and virulence of serotype M28 GAS. We used naturally occurring clinical isolates with rocA polymorphisms (n Z 48), an isogenic rocA deletion mutant strain, and five isogenic rocA polymorphism mutant strains to perform genome-wide transcript analysis (RNA sequencing), in vitro virulence factor assays, and mouse and nonhuman primate pathogenesis studies to test this hypothesis. Results demonstrated that polymorphisms in rocA result in either a subtle transcriptome change, causing a wild-typeelike virulence phenotype, or a substantial transcriptome change, leading to a significantly increased virulence phenotype. Each polymorphism had a unique effect on the global GAS transcriptome. Taken together, our data show that naturally occurring polymorphisms in one gene encoding an accessory protein can significantly alter the global transcriptome and virulence phenotype of GAS, an important human pathogen.

Identification of distinct impacts of CovS inactivation on the transcriptome of acapsular group A streptococci

“…Our finding that the emm 28 strain had lower baseline CovR~P levels relative to emm 87, emm 89, and emm 1 strains adds to growing information regarding the apparently atypical nature of the CovRS system in this particular emm type ( 44 ). Bernard et al noted that emm 28 strains have an unusually high number of RocA polymorphisms relative to other emm types and demonstrated a dramatic impact of RocA on the emm 28 transcriptome ( 85 ). Moreover, an analysis of over 2,000 emm 28 strains identified numerous CovRS polymorphisms that were associated with a markedly altered transcriptome and increased virulence in a mouse necrotizing fasciitis model ( 44 ).…”

RocA Regulates Phosphatase Activity of Virulence Sensor CovS of Group A Streptococcus in Growth Phase- and pH-Dependent Manners

“…These results suggest that the difference between emm 1 and emm 3 strains would be caused, at least partially, by the truncation of the rocA allele in the emm 3 strains. The truncated rocA alleles were found in the emm 3 and emm 18 isolates; in addition, the variations in the amino acid sequence of RocA among the emm 28 isolates and in the number of tandem repeats in the promoter regions of rocA gene found in different emm 89 isolates are associated with the changes of the regulatory activity of RocA and the expression level of rocA , respectively ( 24 – 26 ). These changes would result in the diverse responses when GAS invades into a niche with neutral pH conditions (e.g., blood) during infection and could be significantly associated with bacterial invasiveness.…”

Genome-Wide Screens Identify Group A Streptococcus Surface Proteins Promoting Female Genital Tract Colonization and Virulence

“…Quantitative RT-PCR analysis of emm28 expression was performed according to previous descriptions. 46,47 Briefly, GAS strains were grown in quadruplicate in THY broth to midexponential phase (OD600 Z 0.5). RNA was extracted from GAS culture using the RNeasy kit (Qiagen, Hilden, Germany).…”