Regulation of leukotoxin in leukotoxic and nonleukotoxic strains of Actinobacillus actinomycetemcomitans.
AUTOR(ES)
Spitznagel, J
RESUMO
Actinobacillus actinomycetemcomitans is a gram-negative bacterium that has been implicated in the etiology of several forms of periodontitis, especially localized juvenile periodontitis. A potent leukotoxin (Lkt) is produced by most A. actinomycetemcomitans isolates from patients with periodontal disease, but some isolates are leukotoxin nonproducing (Lkt-). The molecular bases for the differences in leukotoxin expression are being explored to clarify the role of leukotoxin in pathogenesis. We have previously cloned the leukotoxin structural gene, lktA, from the leukotoxin-producing (Lkt+) strain JP2 and have shown that it is linked to three other genes, lktB, lktC, and lktD, whose gene products are thought to be required for activation and localization of the leukotoxin. These genes have now been used in Southern blot analysis to demonstrate that Lkt- strains, like Lkt+ strains, contain all four genes of the lkt gene cluster. While restriction fragment length polymorphisms were detected, they did not correlate with toxin phenotype. RNA blot analysis demonstrated that Lkt+ strains produced two transcripts, one 9.3 kb in length and the other 4.3 kb. They encode lktCABD and lktCA. respectively. Lkt- strains contained significantly lower levels of the 4.3-kb transcript with no discernible 9.3-kb message. The leukotoxic activity of the A. actinomycetemcomitans strains, measured by chromium release assays, correlated with the lkt RNA content. Therefore, a major component of leukotoxin regulation is at the level of RNA transcription or stability. Interestingly, the lkt RNAs in JP2 are regulated during growth phase, being greatly reduced in cells approaching stationary phase. Thus, the regulation of lkt RNA can be affected by both genotype and environment.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=257855Documentos Relacionados
- Differential regulation of the leukotoxin operon in highly leukotoxic and minimally leukotoxic strains of Actinobacillus actinomycetemcomitans.
- Regulation of Actinobacillus actinomycetemcomitans leukotoxin expression: analysis of the promoter regions of leukotoxic and minimally leukotoxic strains.
- Monoclonal antibodies to leukotoxin of Actinobacillus actinomycetemcomitans.
- Cloning and expression of the leukotoxin gene from Actinobacillus actinomycetemcomitans.
- Characterization of an inducible bacteriophage from a leukotoxic strain of Actinobacillus actinomycetemcomitans.