Defining the Mga regulon: comparative transcriptome analysis reveals both direct and indirect regulation by Mga in the group A streptococcus

Abstract

SummaryThe regulator Mga in the group A streptococcus (GAS) is known to directly activate several virulence genes important for colonization and immune evasion. Transcriptome analysis comparing two mga-1 serotypes (M1 SF370, M6 JRS4) and one mga-2 serotype (M4 GA40634) against their isogenic mga-inactivated strains uncovered a broader Mga regulon profile containing both activated and repressed genes with predicted functions primarily related to sugar metabolism. This was reflected in the altered abilities of M1 and M4 Mga mutants to grow in chemically defined media with a single sugar source compared with their wild-type counterparts. Although the M1 and M4 Mga profiles were similar, the M6 JRS4 was clearly distinct, even from other M6 strains. Real-time RT-PCR and Northern blots confirmed that established core Mga regulon genes directly activated by Mga (emm, scpA, sof, fba) exhibited the highest activation levels across all strains tested. Spy2036 encoding a cytosolic hypothetical protein was highly activated in all three serotypes and was called gene regulated by Mga (grm). Mga bound directly to Pgrm, which overlaps the Mga-regulated Psof in OF + strains, suggesting that grm is part of the core Mga regulon and Mga is able to activate divergently transcribed genes from a single site. Furthermore, Mga activated speB when detectable in the wild-type strain, although direct binding of Mga to PspeB could not be demonstrated. Thus, Mga is able to both directly and indirectly regulate genes shown to be important for virulence and the metabolic homeostasis of GAS.

Effects of the ERES Pathogenicity Region Regulator Ralp3 on Streptococcus pyogenes Serotype M49 Virulence Factor Expression

“…However, the lac1 operon seems to be involved in virulence gene regulation (25). Furthermore, Mga influences directly or indirectly over 10% of the GAS transcriptome, including genes encoded for sugar utilization, e.g., the fru operon (31). The knockout of ralp3 resulted in a reduction in the transcript levels of Mga, which in turn could lead to reduced transcription of the fru operon.…”

TrxR, a New CovR-Repressed Response Regulator That Activates the Mga Virulence Regulon in Group A Streptococcus

“…Microarray experiments were performed as previously described (35). Briefly, total RNA from three biological replicates was isolated from MGAS5005 and the isogenic trxR mutant strain MGAS5005.trxR containing the empty vector pJRS525 at late logarithmic phase (100 Klett units) using a Triton X-100 isolation protocol (44).…”

A decade of molecular pathogenomic analysis of group A Streptococcus

“…Similarly, there are more than 100 putative stand-alone transcriptional regulators encoded within the GAS genome, only a few of which had been identified before the availability of a genome sequence. Of the 100 putative stand-alone transcriptional regulators, 12 have now been investigated in detail, and the transcriptomes that eight of these regulate in vitro have been determined (17,(63)(64)(65)(66)(67)(68).…”