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IS195, an insertion sequence-like element associated with protease genes in Porphyromonas gingivalis.

ABSTRACT: Porphyromonas gingivalis is recognized as an important etiologic agent in adult and early-onset periodontal disease. Proteases produced by this organism contribute to its virulence in mice. Protease-encoding genes have been shown to contain multiple copies of repeated nucleotide sequences. These conserved sequences have also been found in hemagglutinin genes. In the process of studying the genetic loci containing the conserved repeated sequences, we have characterized a prtP gene homolog from P. gingivalis W83 encoding a cysteine protease with Lys-X specificity. However, this prtP gene was interrupted by an insertion sequence-like element which we designated IS195. Furthermore, IS195 and another element, IS1126, were present downstream of prtP gene homologs (kgp) found in P. gingivalis H66 and 381. IS195, a 1,068-bp insertion sequence-like element, contained 11-bp inverted repeats at its termini and was bordered by 9-bp direct repeats presumed to be a transposition-mediated target site duplication. Its central region contained one large open reading frame encoding a predicted 300-amino-acid protein which appeared to be a transposase. We isolated two naturally occurring variants of P. gingivalis W83, one carrying IS195 within the coding region of the prtP gene and another containing an intact prtP gene. Biochemical characterization revealed a lack of trypsin-like Lys-X specific proteolytic activity in the P. gingivalis W83 variant carrying the disrupted prtP gene. Studies using a mouse model revealed a reduction of virulence resulting from insertion of IS195 into the coding region of the prtP gene. An allelic-exchange mutant defective in the prtP gene also was constructed and tested in vivo. It displayed intermediate virulence compared to that of the wild-type and prtP::IS195 mutant strains. We conclude that the Lys-X cysteine protease contributes to virulence in soft tissue infections.

SUBMITTER: Lewis JP

PROVIDER: S-EPMC108310 | biostudies-literature | 1998 Jul

REPOSITORIES: biostudies-literature

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IS195, an insertion sequence-like element associated with protease genes in Porphyromonas gingivalis.

Lewis J P JP Macrina F L FL

Infection and immunity 19980701 7

Porphyromonas gingivalis is recognized as an important etiologic agent in adult and early-onset periodontal disease. Proteases produced by this organism contribute to its virulence in mice. Protease-encoding genes have been shown to contain multiple copies of repeated nucleotide sequences. These conserved sequences have also been found in hemagglutinin genes. In the process of studying the genetic loci containing the conserved repeated sequences, we have characterized a prtP gene homolog from P. ...[more]

PMID: 9632563

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Project description:We have previously reported on a Tn4351-generated mutant of Porphyromonas gingivalis (MSM-3) which expresses enhanced arginine-specific proteinase activity and does not utilize hemin or hemoglobin for growth (C. A. Genco et al., Infect. Immun. 63:2459-2466, 1995). In the process of characterizing the genetic lesion in P. gingivalis MSM-3, we have determined that the endogenous P. gingivalis insertion sequence element IS1126 is capable of transposition within P. gingivalis. We have also determined that IS1126 transposition modulates the transcription of the genes encoding the lysine-specific proteinase, gingipain K (kgp) and the arginine-specific proteinase, gingipain R2 (rgpB). Sequence analysis of P. gingivalis MSM-3 revealed that Tn4351 had inserted 60 bp upstream of the P. gingivalis endogenous IS element IS1126. Furthermore, P. gingivalis MSM-3 exhibited two additional copies of IS1126 compared to the parental strain A7436. Examination of the first additional IS1126 element, IS1126(1), indicated that it has inserted into the putative promoter region of the P. gingivalis kgp gene. Analysis of total RNA extracted from P. gingivalis MSM-3 demonstrated no detectable kgp transcript; likewise, P. gingivalis MSM-3 was devoid of lysine-specific proteinase activity. The increased arginine-specific proteinase activity exhibited by P. gingivalis MSM-3 was demonstrated to correlate with an increase in the rgpA and rgpB transcripts. The second additional IS1126 element, IS1126(2), was found to have inserted upstream of a newly identified gene, hmuR, which exhibits homology to a number of TonB-dependent genes involved in hemin and iron acquisition. Analysis of total RNA from P. gingivalis MSM-3 demonstrated that hmuR is transcribed, indicating that the insertion of IS1126 had not produced a polar effect on hmuR transcription. The hemin-hemoglobin defect in P. gingivalis MSM-3 is proposed to result from the inactivation of Kgp, which has recently been demonstrated to function in hemoglobin binding. Taken together, the results presented here demonstrate that the introduction of Tn4351 into the P. gingivalis chromosome has resulted in two previously undocumented phenomena in P. gingivalis: (i) the transposition of the endogenous insertion sequence element IS1126 and (ii) the modulation of gingipain transcription and translation as a result of IS1126 transposition.

Dataset Information

IS195, an insertion sequence-like element associated with protease genes in Porphyromonas gingivalis.

Publications

IS195, an insertion sequence-like element associated with protease genes in Porphyromonas gingivalis.

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