# Role of response regulator phosphorylation in group A streptococcal pathogenesis

> **NIH NIH R01** · UNIVERSITY OF TX MD ANDERSON CAN CTR · 2021 · $400,000

## Abstract

PROJECT SUMMARY:
The ability of bacteria to modify gene expression in adaptation to environmental cues is a key component of
bacterial pathogenesis. Two component gene regulatory systems (TCS), which generally consist of a
membrane-embedded sensor kinase that alters phosphorylation and dimerization status of its cognate
response regulator in reaction to various stimuli, are a central mechanism by which bacteria adjust expression
of a diverse array of genes. The control of virulence regulator (CovR) of the major human pathogen group A
Streptococcus (GAS) is a model system for understanding how TCS proteins influence bacterial infectivity.
Phosphorylated CovR (CovR~P) primarily serves to repress virulence factor production such that hypervirulent
GAS strains with decreased CovR~P levels emerge during human infection and following experimental mouse
challenge. It was recently shown that inactivation of the control of virulence sensor kinase (CovS) reduces
CovR~P and that CovR~P levels vary between GAS strains of different M serotypes. The goals of this project
are to delineate how changes in CovR~P levels impact GAS pathogenesis and to determine the molecular
mechanisms by which differences in CovR~P levels alter GAS global gene expression. In aim 1, the effect of
CovR~P variation on GAS virulence and the emergence of hypervirulent GAS strains will be evaluated in two
murine models using a series of isoallelic strains that have defined CovR~P levels due to engineered single
amino acid substitutions in either CovR or CovS. Identified variation in virulence will be correlated with global
gene expression profiles to determine mechanisms by which CovR~P alterations influence GAS infectivity.
Specific Aim 2 will seek to decipher the specific role of CovR phosphorylation and dimerization in the regulation
of CovR-controlled genes that differ in their response to varying CovR~P levels. To this end, we will employ in
vivo protein-protein interaction assays to identify co-factors that interact with CovR isoforms that have defined
phosphorylation and dimerization characteristics. The effect of these interactions on CovR-mediated
expression for genes belonging to various sub-groups will be verified using in vitro transcription assays. In aim
3, we will generate the first in vivo analysis of CovR-DNA interaction via a ChIP-Seq approach. Actual
visualization of CovR-DNA complexes using atomic force microscopy will be used to test the hypothesis that
CovR~P differentially interacts with distinct arrangements of cis-regulatory elements found in the promoter
regions of virulence factor encoding genes belonging to the different subgroups of CovR-regulated genes
noted in Specific Aim 2. Given that CovR belongs to the large OmpR/PhoB family of bacterial transcription
factors, completion of the proposed research will significantly augment understanding of the mechanistic basis
by which TCS impact bacterial pathogenesis.

## Key facts

- **NIH application ID:** 10076759
- **Project number:** 5R01AI125292-05
- **Recipient organization:** UNIVERSITY OF TX MD ANDERSON CAN CTR
- **Principal Investigator:** SAMUEL A SHELBURNE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $400,000
- **Award type:** 5
- **Project period:** 2017-01-16 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10076759

## Citation

> US National Institutes of Health, RePORTER application 10076759, Role of response regulator phosphorylation in group A streptococcal pathogenesis (5R01AI125292-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10076759. Licensed CC0.

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