The virR/virS locus regulates the transcription of genes encoding extracellular toxin production in Clostridium perfringens.
Extracellular toxin production in Clostridium perfringens is positively regulated by the two-component regulatory genes virR and virS. Northern (RNA) blots carried out with RNA preparations from the wild-type strain 13 and the isogenic virR and virS mutants TS133 and JIR4000 showed that the virR and virS genes composed an operon and were transcribed as a single 2.1-kb mRNA molecule. Primer extension analysis led to the identification of two promoters upstream of virR. Hybridization analysis of the mutants and their complemented derivatives showed that the virR/virS system positively regulated the production of alpha-toxin (or phospholipase C, theta-toxin (perfringolysin O), and kappa-toxin (collagenase) at the transcriptional level. However, the modes of regulation of these genes were shown to differ. The theta-toxin structural gene, pfoA, had both a major and a very minor promoter, with the major promoter being virR/virS dependent. The colA gene, which encodes the kappa-toxin, had two major promoters, only one of which was virR/virS-dependent. In contrast, the alpha-toxin structural gene, p1c, had only one promoter, which was shown to be partially regulated by the virR and virS genes. Comparative analysis of the virR/virS-dependent promoters did not reveal any common sequence motifs that could represent VirR-binding sites. It was concluded that either the virR/virS system modulates its effects via secondary regulatory genes that are specific for each toxin structural gene or the VirR protein does not have a single consensus binding sequence.
Ba-Thein
W
W
Department of Microbiology, Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan.
Lyristis
M
M
Ohtani
K
K
Nisbet
I T
IT
Hayashi
H
H
Rood
J I
JI
Shimizu
T
T
D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D003016:Clostridium perfringens / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D018085:Regulon / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors; C068267:mry protein, Streptococcus pyogenes