Previous Article | Next Article ![]()
Journal of Bacteriology, September 1999, p. 5373-5383, Vol. 181, No. 17
Department of Microbiology and Immunology,
Rollins Research Center, Emory University, Atlanta, Georgia 30322
Received 22 April 1999/Accepted 25 June 1999
Transcription of mga, encoding the multiple virulence
gene regulator of the group A streptococcus, is positively
autoregulated. This regulation requires a DNA region (Pmga) that
contains both a promoter proximal to mga (P2) and a
promoter located further upstream (P1). To determine if Mga has a
direct role in this process, its ability to bind to specific sequences
within Pmga was tested. A purified fusion of Mga to the C-terminal end
of maltose-binding protein (MBP-Mga), encoded by malE-mga,
was shown previously to bind to the promoter regions of Mga-regulated
genes, including scpA and emm. We report here
that MBP-Mga can function in vivo to regulate emm and
mga. Electrophoretic mobility shift assays and DNase I
footprinting were used to demonstrate specific binding of MBP-Mga to
two ca. 59-bp binding sites in Pmga centered around bases
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Regulation of mga Transcription in the
Group A Streptococcus: Specific Binding of Mga within Its Own Promoter
and Evidence for a Negative Regulator

108 and
180 from the major P2 start of transcription. Mga binding sites from
Pemm and PscpA were shown to compete for binding at the two Pmga sites,
suggesting that the same domain of Mga interacts at all of these
promoter targets. Deletion of the distal Pmga binding site (site I) in
vivo resulted in loss of Mga-dependent transcription from the P2 start.
However, the same lesion resulted in an increase in P1 transcription
that was independent of Mga. This suggests the existence of a repressor of mga transcription with a binding site overlapping those
of Mga.
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Rollins Research Center, Emory University, Atlanta, GA 30322. Phone: (404) 727-0402. Fax: (404) 727-8999. E-mail:
scott{at}microbio.emory.edu.
Present address: Department of Microbiology, The University of
Texas Southwestern Medical Center, Dallas, TX 75325-9048.
This article has been cited by other articles:
| Appl. Environ. Microbiol. | Infect. Immun. | Eukaryot. Cell |
|---|---|---|
| Mol. Cell. Biol. | J. Virol. | Microbiol. Mol. Biol. Rev. |
| ALL ASM JOURNALS |