Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydrolysis of urea by ureases of oral bacteria in dental plaque can cause a considerable increase in plaque pH, which can inhibit the development of dental caries. There is also indirect evidence that urea metabolism may promote the formation of calculus and that ammonia release from urea could exacerbate periodontal diseases. Actinomyces naeslundii, an early colonizer of the oral cavity and a numerically significant plaque constituent, demonstrates comparatively low levels of urease activity on isolation, so this organism has not been considered a major contributor to total oral urease activity. In this study it was observed that urease activity and urease-specific mRNA levels in A. naeslundii WVU45 can increase up to 50-fold during growth under nitrogen-limiting conditions. Using primer extension analysis, a putative, proximal, nitrogen-regulated promoter of the A. naeslundii urease gene cluster was identified. The functionality and nitrogen responsiveness of this promoter were confirmed using reporter gene fusions and 5' deletion analysis. The data indicated that regulation of urease expression by nitrogen availability in A. naeslundii may require a positive transcriptional activator. Plaque bacteria may experience nitrogen limitation when carbohydrates are present in excess. Therefore, based on the results of this study and in contrast to previous beliefs, strains of A. naeslundii may have the potential to be significant contributors to total plaque ureolysis, particularly during periods when there is an increased risk for caries development.
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PMID:Analysis of urease expression in Actinomyces naeslundii WVU45. 1108 80

Streptococcus mutans, the primary causative agent of human dental caries, contains a single copy of the gene encoding ClpP, the chief intracellular protease responsible for tolerance to various environmental stresses. To better understand the role of ClpP in stress response, we investigated the regulation of clpP expression in S. mutans. Using semiquantitative reverse transcription-PCR analysis, we observed that, under nonstressed conditions, clpP expression is somewhat constant throughout the growth phases, although it gradually decreases as cells enter the late stationary phase. The half-life of the clpP transcript was found to be less than 1 minute. Sequence analysis of the clpP locus reveals the presence of a 50-bp tandem repeat sequence located immediately upstream of the clpP promoter (PclpP). PCR and DNA sequence analyses suggest that the number of tandem repeat units can vary from as few as two to as many as nine, depending on the particular S. mutans isolate. Further analysis, using a transcriptional reporter fusion consisting of PclpP fused to a promoterless gusA gene, indicates that the presence of the repeat sequence region within PclpP results in an approximately fivefold increase in expression from PclpP compared to the repeat-free transcriptional reporter fusion. CtsR, a transcriptional repressor that negatively regulates clpP expression, has no effect on this repeat-mediated induction of clpP transcription. Furthermore, the repeat sequence is not necessary for the induction of clpP under stress conditions. Database searches indicate that the region containing the tandem repeats is absent in the clpP loci in other bacteria, including other closely related Streptococcus spp., suggesting that the repeat sequences are specific for the induction of clpP expression in S. mutans. We speculate that a host-specific transcriptional activator might be involved in the upregulation of clpP expression in S. mutans.
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PMID:Transcription of clpP is enhanced by a unique tandem repeat sequence in Streptococcus mutans. 1904 52