Functional Analysis of the Heat Shock Regulator HrcA of<i>Chlamydia trachomatis</i>

Wilson, Adam C.; Tan, Ming

doi:10.1128/jb.184.23.6566-6571.2002

Cited by 52 publications

(78 citation statements)

References 26 publications

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“…As indicated in Fig. 7, chlamydial HrcA readily interacts with the promoter region of dnaK of M. genitalium (lane 2), which was comparable to the interaction between chlamydial HrcA and its own dnaK promoter (lane 2) (46). Moreover, the addition of unlabeled competitors markedly reduced the DNA-protein complex formation (lanes 3).…”

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confidence: 77%

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

2006

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Mycoplasma genitalium is a human bacterial pathogen linked to urethritis and other sexually transmitted diseases as well as respiratory and joint pathologies. Though its complete genome sequence is available, little is understood about the regulation of gene expression in this smallest known, self-replicating cell, as its genome lacks orthologues for most of the conventional bacterial regulators. Still, the transcriptional repressor HrcA (heat regulation at CIRCE [controlling inverted repeat of chaperone expression]) is predicted in the M. genitalium genome as well as three copies of its corresponding regulatory sequence CIRCE. We investigated the transcriptional response of M. genitalium to elevated temperatures and detected the differential induction of four hsp genes. Three of the up-regulated genes, which encode DnaK, ClpB, and Lon, possess CIRCE within their promoter regions, suggesting that the HrcA-CIRCE regulatory mechanism is functional. Additionally, one of three DnaJ-encoding genes was up-regulated, even though no known regulatory sequences were found in the promoter region. Transcript levels returned to control values after 1 h of incubation at 37°C, reinforcing the transient nature of the heat shock transcriptional response. Interestingly, neither of the groESL operon genes, which encode the GroEL chaperone and its cochaperone GroES, responded to heat shock. These data suggest that M. genitalium selectively regulates a limited number of genes in response to heat shock.

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confidence: 77%

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

2006

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“…The location of the Group III chaperonin downstream of the hrcA suggested that Group III CPNs could be HrcA regulated. The Group I CPN and Hsp70s of many bacteria are HrcA regulated (27)(28)(29)(30). In silico analysis revealed the presence of a CIRCE consensus site upstream of the HrcA as well as the Group I CPN in these genomes (Fig.…”

Section: Resultsmentioning

confidence: 99%

Archaeal-like chaperonins in bacteria

Techtmann

Robb

2010

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

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Chaperonins (CPN) are ubiquitous oligomeric protein machines that mediate the ATP-dependent folding of polypeptide chains. These chaperones have not only been assigned stress response and normal housekeeping functions but also have a role in certain human disease states. A longstanding convention divides CPNs into two groups that share many conserved sequence motifs but differ in both structure and distribution. Group I complexes are the well known GroEL/ES heat-shock proteins in bacteria, that also occur in some species of mesophilic archaea and in the endosymbiotic organelles of eukaryotes. Group II CPNs are found only in the cytosol of archaea and eukaryotes. Here we report a third, divergent group of CPNs found in several species of bacteria. We propose to name these Group III CPNs because of their distant relatedness to both Group I and II CPNs as well as their unique genomic context, within the hsp70 operon. The prototype Group III CPN, Carboxydothermus hydrogenoformans chaperonin ( Ch -CPN), is able to refold denatured proteins in an ATP-dependent manner and is structurally similar to the Group II CPNs, forming a 16-mer with each subunit contributing to a flexible lid domain. The Group III CPN represent a divergent group of bacterial CPNs distinct from the GroEL/ES CPN found in all bacteria. The Group III lineage may represent an ancient horizontal gene transfer from an archaeon into an early Firmicute lineage. An analysis of their functional and structural characteristics may provide important insights into the early history of this ubiquitous family of proteins.

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“…Knowledge of the extent to which the regulation of transcription contributes to the chlamydial life cycle has been limited, in part, by the lack of suitable experimental tools. In this regard, only a handful of transcription inhibitors (21)(22)(23)(24)(25) and three transcription activators (26)(27)(28) had been identified in chlamydiae before our study. Our work identifies GrgA as a previously undocumented transcription factor in C. trachomatis.…”

Section: Discussionmentioning

confidence: 99%

Chlamydia trachomatis protein GrgA activates transcription by contacting the nonconserved region of σ ⁶⁶

Bao¹,

Nickels

Fan³

2012

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

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The bacterial RNA polymerase holoenzyme consists of a catalytic core enzyme in complex with a σ factor that is required for promoter-specific transcription initiation. Primary, or housekeeping, σ factors are responsible for most of the gene expression that occurs during the exponential phase of growth. Primary σ factors share four regions of conserved sequence, regions 1-4, which have been further subdivided. Many primary σ factors also contain a nonconserved region (NCR) located between subregions 1.2 and 2.1, which can vary widely in length. Interactions between the NCR of the primary σ factor of Escherichia coli, σ 70 , and the β′ subunit of the E. coli core enzyme have been shown to influence gene expression, suggesting that the NCR of primary σ factors represents a potential target for transcription regulation. Here, we report the identification and characterization of a previously undocumented Chlamydia trachomatis transcription factor, designated GrgA (general regulator of genes A). We demonstrate in vitro that GrgA is a DNA-binding protein that can stimulate transcription from a range of σ 66 -dependent promoters. We further show that GrgA activates transcription by contacting the NCR of the primary σ factor of C. trachomatis, σ 66 . Our findings suggest GrgA serves as an important regulator of σ 66 -dependent transcription in C. trachomatis. Furthermore, because GrgA is present only in chlamydiae, our findings highlight how nonconserved regions of the bacterial RNA polymerase can be targets of regulatory factors that are unique to particular organisms.

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Functional Analysis of the Heat Shock Regulator HrcA ofChlamydia trachomatis

Cited by 52 publications

References 26 publications

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

Archaeal-like chaperonins in bacteria

Chlamydia trachomatis protein GrgA activates transcription by contacting the nonconserved region of σ ⁶⁶

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Functional Analysis of the Heat Shock Regulator HrcA ofChlamydia trachomatis

Cited by 52 publications

References 26 publications

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

Transcriptional Heat Shock Response in the Smallest Known Self-Replicating Cell,Mycoplasma genitalium

Archaeal-like chaperonins in bacteria

Chlamydia trachomatis protein GrgA activates transcription by contacting the nonconserved region of σ 66

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Chlamydia trachomatis protein GrgA activates transcription by contacting the nonconserved region of σ ⁶⁶