In vivoandin vitroStudies of TrpR-DNA Interactions

Yang, Jie; Gunasekera, Angelo; Lavoie, T. A.; Jin, Lihua; Lewis, Dale E.A.; Carey, Jannette

doi:10.1006/jmbi.1996.0232

Cited by 38 publications

(33 citation statements)

References 57 publications

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“…3A, lanes 1 to 8). The gel shift complex consisted of at least four lowermobility bands, which is consistent with the observation in E. coli that there is oligomerization of TrpR dimers at the trp operator (4,15,40). Addition of polyclonal anti-TrpR antibodies produced a supershift, indicating that the binding was due to TrpR (Fig.…”

Section: Resultssupporting

confidence: 88%

Molecular Mechanism of Tryptophan-Dependent Transcriptional Regulation inChlamydia trachomatis

Akers¹,

Tan

2006

J Bacteriol

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Tryptophan is an essential amino acid that is required for normal development in Chlamydia species, and tryptophan metabolism has been implicated in chlamydial persistence and tissue tropism. The ability to synthesize tryptophan is not universal among the Chlamydiaceae, but species that have a predicted tryptophan biosynthetic pathway also encode an ortholog of TrpR, a regulator of tryptophan metabolism in many gram-negative bacteria. We show that in Chlamydia trachomatis serovar D, TrpR regulates its own gene and trpB and trpA, the genes for the two subunits of tryptophan synthase. These three genes form an operon that is transcribed by the major form of chlamydial RNA polymerase. TrpR acts as a tryptophan-dependent aporepressor that binds specifically to operator sequences upstream of the trpRBA operon. We also found that TrpR repressed in vitro transcription of trpRBA in a promoter-specific manner, and the level of repression was dependent upon the concentrations of TrpR and tryptophan. Our findings provide a mechanism for chlamydiae to sense changes in tryptophan levels and to respond by modulating expression of the tryptophan biosynthesis genes, and we present a unified model that shows how C. trachomatis can combine transcriptional repression and attenuation to regulate intrachlamydial tryptophan levels. In the face of host defense mechanisms that limit tryptophan availability from the infected cell, the ability to maintain homeostatic control of intrachlamydial tryptophan levels is likely to play an important role in chlamydial pathogenesis.

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Section: Resultssupporting

confidence: 88%

Molecular Mechanism of Tryptophan-Dependent Transcriptional Regulation inChlamydia trachomatis

Akers¹,

Tan

2006

J Bacteriol

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“…The aroH operon specifies one of three nearly identical enzymes (the other two are specified by aroF and aroG) that catalyze the first reaction in the common pathway of aromatic amino acid biosynthesis (12). The mtr operon encodes a tryptophan-specific permease (13,14), the trpR operon encodes the trp aporepressor (15,16), and the aroL operon encodes one of two enzymes that catalyze the same reaction in the common aromatic pathway (17,18). The mtr and aroL operons are also transcriptionally regulated by TyrR, the general aromatic pathway regulatory protein (2).…”

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confidence: 99%

DNA microarray analysis of gene expression in response to physiological and genetic changes that affect tryptophan metabolism in Escherichia coli

Khodursky

Peter

Cozzarelli

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

178

133

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We investigated the global changes in mRNA abundance in Escherichia coli elicited by various perturbations of tryptophan metabolism. To do so we printed DNA microarrays containing 95% of all annotated E. coli ORFs. We determined the expression profile that is predominantly dictated by the activity of the tryptophan repressor. Only three operons, trp, mtr, and aroH, exhibited appreciable expression changes consistent with this profile. The quantitative changes we observed in mRNA levels for the five genes of the trp operon were consistent within a factor of 2, with expectations based on established Trp protein levels. Several operons known to be regulated by the TyrR protein, aroF-tyrA, aroL, aroP, and aroG, were down-regulated on addition of tryptophan. TyrR can be activated by any one of the three aromatic amino acids. Only one operon, tnaAB, was significantly activated by the presence of tryptophan in the medium. We uncovered a plethora of likely indirect effects of changes in tryptophan metabolism on intracellular mRNA pools, most prominent of which was the sensitivity of arginine biosynthetic operons to tryptophan starvation.trp regulon ͉ transcription ͉ gene regulation

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“…Inhibition of transcription by preventing TBP access to the TATA box region has also been documented for the Lrs14 repressor from Sulfolobus solfataricus (9,33) and TrmB repressor in Thermococcus litoralis (29). This mechanism of repression seems formally analogous to operator binding by bacterial repressors, including TrpR (35,43,52), preventing sigma factor-directed promoter binding by bacterial RNAPs. But sigma factors dissociate from the DNA following departure of the RNAP, resetting the competition between repressor and RNAP, whereas archaeal TBP may remain bound to the TATA box region after initiation (51).…”

Section: Discussionmentioning

confidence: 77%

“…TrpY synthesis as a sensor of charged tRNA Trp availability. As discussed below, TrpY is a tryptophan-responsive regulator of transcription of trp genes and, in this regard, functions in a manner superficially similar to TrpR in E. coli (14,35,43,52,53). There is, however, no evidence for a common ancestry, and the archaeal gene and protein were designated trpY and TrpY to avoid any inference of homology in ancestry or detailed mechanism of function with TrpR.…”

Section: Discussionmentioning

confidence: 99%

“…An interesting evolutionary issue is that although the trp genes themselves are conserved in all three biological domains, a variety of very different mechanisms regulate their expression, with regulation often imposed at more than one level (26,48,53). In Escherichia coli, for example, when the tryptophan pool is sufficient, TrpR, a tryptophan-activated repressor, binds upstream of the trpEGCBA operon blocking RNA polymerase (RNAP) access to the promoter (35,43,52,53). If initiation nevertheless does occur, regulation is then imposed during translation of a short leader peptide (TrpL).…”

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Regulation of Tryptophan Operon Expression in the Archaeon Methanothermobacter thermautotrophicus

Xie

Reeve

2005

J Bacteriol

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Conserved trp genes encode enzymes that catalyze tryptophan biosynthesis in all three biological domains, and studies of their expression in Bacteria and eukaryotes have revealed a variety of different regulatory mechanisms. The results reported here provide the first detailed description of an archaeal trp gene regulatory system. We have established that the trpEGCFBAD operon in Methanothermobacter thermautotrophicus is transcribed divergently from a gene (designated trpY) that encodes a tryptophan-sensitive transcription regulator. TrpY binds to TRP box sequences (consensus, TGTACA) located in the overlapping promoter regions between trpY and trpE, inhibiting trpY transcription in the absence of tryptophan and both trpY and trpEGCFBAD transcription in the presence of tryptophan. TrpY apparently inhibits trpY transcription by blocking RNA polymerase access to the site of trpY transcription initiation and represses trpEGCFBAD transcription by preventing TATA box binding protein (TBP) binding to the TATA box sequence. Given that residue 2 (W2) is the only tryptophan in TrpY and in TrpY homologues in other Euryarchaea and that there is only one tryptophan codon in the entire trpEGCFBAD operon (trpB encodes W175), expression of the trp operon may also be regulated in vivo by the supply of charged tRNA Trp available to translate the second codon of the trpY mRNA.The biosynthesis of tryptophan from chorismate is catalyzed by enzymes with a common ancestry in Bacteria, Archaea, eukaryotic microorganisms, and plants (14,26,31,48). This pathway is metabolically very expensive, and expression of the trp genes that encode the enzymes that catalyze tryptophan biosynthesis is therefore tightly regulated (48). An interesting evolutionary issue is that although the trp genes themselves are conserved in all three biological domains, a variety of very different mechanisms regulate their expression, with regulation often imposed at more than one level (26,48,53). In Escherichia coli, for example, when the tryptophan pool is sufficient, TrpR, a tryptophan-activated repressor, binds upstream of the trpEGCBA operon blocking RNA polymerase (RNAP) access to the promoter (35,43,52,53). If initiation nevertheless does occur, regulation is then imposed during translation of a short leader peptide (TrpL). With the availability of charged tRNA Trp adequate for efficient TrpL translation, transcription is terminated by attenuation upstream of trpE (54). Similarly, in Bacillus subtilis, two sequential events in trp gene expression are regulated by the availability of tryptophan. With an adequate supply of tryptophan, transcription of the trpEDCFBA genes is prevented by attenuation but not as a consequence of efficient leader-peptide translation. Instead, the trp transcript is bound by a tryptophan-activated RNA-binding protein, TRAP, preventing the formation of an antiterminator and allowing attenuation. If trp operon transcription escapes attenuation, tryptophan-activated TRAP binds to the mRNA, and this sequesters the trpE ribosome bindin...

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In vivoandin vitroStudies of TrpR-DNA Interactions

Cited by 38 publications

References 57 publications

Molecular Mechanism of Tryptophan-Dependent Transcriptional Regulation inChlamydia trachomatis

Molecular Mechanism of Tryptophan-Dependent Transcriptional Regulation inChlamydia trachomatis

DNA microarray analysis of gene expression in response to physiological and genetic changes that affect tryptophan metabolism in Escherichia coli

Regulation of Tryptophan Operon Expression in the Archaeon Methanothermobacter thermautotrophicus

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