Multiple-Level Regulation of Genes for Protocatechuate Degradation in
            <i>Acinetobacter baylyi</i>
            Includes Cross-Regulation

Siehler, Simone Yasmin; Dal, Siireyya; Fischer, Rita; Patz, Patricia; Gerischer, Ulrike

doi:10.1128/aem.01608-06

Cited by 24 publications

(39 citation statements)

References 38 publications

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“…The pcaUp promoter, which controls the expression of the pcaU regulatory gene belonging to the IclR family, is also subject to catabolic repression, but the molecular mechanism remains unknown (Dal et al, 2002;Siehler et al, 2007). Taking our results together with previous data (Torres et al, 2003) we have demonstrated that the glucose effect on mhp expression is exerted at the level of both catabolic and regulatory promoters.…”

Section: Discussionsupporting

confidence: 64%

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Escherichia coli mhpR gene expression is regulated by catabolite repression mediated by the cAMP–CRP complex

2011

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The expression of the mhp genes involved in the degradation of the aromatic compound 3-(3-hydroxyphenyl)propionic acid (3HPP) in Escherichia coli is dependent on the MhpR transcriptional activator at the Pa promoter. This catabolic promoter is also subject to catabolic repression in the presence of glucose mediated by the cAMP-CRP complex. The Pr promoter drives the MhpR-independent expression of the regulatory gene. In vivo and in vitro experiments have shown that transcription from the Pr promoter is downregulated by the addition of glucose and this catabolic repression is also mediated by the cAMP-CRP complex. The activation role of the cAMP-CRP regulatory system was further investigated by DNase I footprinting assays, which showed that the cAMP-CRP complex binds to the Pr promoter sequence, protecting a region centred at position "40.5, which allowed the classification of Pr as a class II CRP-dependent promoter. Open complex formation at the Pr promoter is observed only when RNA polymerase and cAMP-CRP are present. Finally, by in vitro transcription assays we have demonstrated the absolute requirement of the cAMP-CRP complex for the activation of the Pr promoter. INTRODUCTIONThe mhp gene cluster of Escherichia coli, which encodes the 3-hydroxyphenylpropionate (3HPP) catabolic pathway, constitutes a model system for studying bacterial degradation because of its distinctive regulation. The mhp regulatory region contains the Pr and Pa promoters, which control the expression of the divergently transcribed mhpR regulatory gene and mhp catabolic genes, respectively (Ferrández et al., 1997). Expression of the mhp catabolic genes depends on the transcriptional activator MhpR, which belongs to the IclR family of transcriptional regulators. MhpR behaves as a 3HPP-dependent activator of the Pa promoter by binding to its specific operator sequence centred at position 258 with respect to the transcription start site in the Pa promoter (Fig. 1a) (Ferrández et al., 1997;Torres et al., 2003). MhpR displays a distinctive regulation mechanism in which phenylpropionic acid activates the MhpR regulator synergistically with the true inducers, representing the first case of such an unusual synergistic effect described for a bacterial regulator (Manso et al., 2009). Gene expression from the Pa promoter is also under a strict global control system mediated by the cAMP-CRP complex that allows expression of the mhp catabolic genes when glucose is not available and 3HPP is present in the medium (Torres et al., 2003). The Pa promoter contains a potential CRP-binding site centred at position 295.5 relative to the transcription start point of Pa (Fig. 1a). In vitro experiments revealed that the specific activator, MhpR, is essential for the recruitment of CRP at the Pa promoter (Torres et al., 2003). The synergistic transcription activation by the cAMP-CRP complex and the MhpR activator allowed the Pa promoter of the mhp cluster to be classified as a class III CRP-dependent promoter (Torres et al., 2003).Although the regulation of the mh...

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Escherichia coli mhpR gene expression is regulated by catabolite repression mediated by the cAMP–CRP complex

2011

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“…Thus the differential expression on the noninducing carbon sources investigated here is independent of the induction status, an observation that had been made earlier for the pca-qui operon (Siehler et al, 2007;Trautwein & Gerischer, 2001). …”

Section: The Dca Genes Underlie Catabolite Repressionmentioning

confidence: 64%

“…Since a strong catabolite repression of the pca operon has been shown (Dal et al, 2002;Siehler et al, 2007) we address here the question if other operons linked with aromatic compound catabolism (are, ant, ben, hca, dca) also underlie this regulatory mechanism. To answer this question we produced transcriptional fusions between the catabolic genes and the luc gene, coding for luciferase.…”

Section: Introductionmentioning

confidence: 99%

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Aromatic degradative pathways in Acinetobacter baylyi underlie carbon catabolite repression

2008

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Carbon catabolite repression is an important mechanism allowing efficient carbon source utilization. In the soil bacterium Acinetobacter baylyi, this mechanism has been shown to apply to the aromatic degradative pathways for the substrates protocatechuate, p-hydroxybenzoate and vanillate. In this investigation, transcriptional fusions with the gene for luciferase in the gene clusters for the degradation of benzyl esters, anthranilate, benzoate, hydroxycinnamates and dicarboxylates (are, ant, ben, hca and dca genes) were constructed and established in the chromosome of A. baylyi. The respective strains revealed the presence of strong carbon catabolite repression at the transcriptional level. In all cases, succinate and acetate in combination had the strongest repressing effect, and pyruvate (or lactate in case of the ben and hca genes) allowed the highest expression when these carbon sources were supplied together with the respective inducer. The pattern of repression for the different cosubstrates was similar for all operons investigated and was also observed in the absence of the respective inducing compounds, indicating a mechanism that is independent of the respective specific regulators. Repression by acetate and succinate varied between 88 % for the hca genes and 99 % for the pca genes.

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Regulation of genes in Streptomyces bacteria required for catabolism of lignin-derived aromatic compounds

Davis

Sello

2009

Appl Microbiol Biotechnol

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The major utilization pathway for lignin-derived aromatic compounds in microorganisms is the beta-ketoadipate pathway. Through this pathway, the aromatic compounds protocatechuate and catechol are converted to acetyl coenzyme A and succinyl coenzyme A. The enzymes of the protocatechuate branch of this pathway are encoded by the pca genes. Here, we describe a gene cluster in Streptomyces coelicolor containing the pca structural genes and a regulatory gene required for the catabolism of protocatechuate. We found that transcription of the structural genes in S. coelicolor is induced by protocatechuate and p-hydroxybenzoate. We also observed inducible transcription of pca structural genes in the ligninolytic strain Streptomyces viridosporus ATCC 39115. Disruption of a gene encoding a putative MarR family transcription factor that is divergently transcribed from the pca structural genes resulted in constitutive transcription of the structural genes. Thus, the transcription factor encoded by this gene is an apparent negative regulator of pca gene transcription in S. coelicolor. Our findings suggest how Streptomyces bacteria could be engineered for and used in biotechnology for the utilization and degradation of lignin and lignin-derived aromatic compounds.

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Multiple-Level Regulation of Genes for Protocatechuate Degradation in Acinetobacter baylyi Includes Cross-Regulation

Cited by 24 publications

References 38 publications

Escherichia coli mhpR gene expression is regulated by catabolite repression mediated by the cAMP–CRP complex

Escherichia coli mhpR gene expression is regulated by catabolite repression mediated by the cAMP–CRP complex

Aromatic degradative pathways in Acinetobacter baylyi underlie carbon catabolite repression

Regulation of genes in Streptomyces bacteria required for catabolism of lignin-derived aromatic compounds

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