DNA Supercoiling-Dependent Gene Regulation in
            <i>Chlamydia</i>

Niehus, Eike; Cheng, Elaine; Tan, Ming

doi:10.1128/jb.00431-08

Cited by 36 publications

(33 citation statements)

References 51 publications

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“…The 66 -dependent bioY promoter was transcribed at a higher level from a supercoiled DNA template than from a relaxed template (Fig. 3C), demonstrating supercoiling-dependent promoter activity that is characteristic of chlamydial midcycle genes (7,11). We propose to call this new 66 promoter bioY P1 and to call the original 28 promoter bioY P2, reflecting the location of P1 upstream of P2 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For example, chlamydial genes with supercoiling-responsive promoters have been proposed to be upregulated in midcycle by increased chlamydial DNA supercoiling levels at this stage of the developmental cycle (7,8,11). In contrast, late genes have been proposed to be repressed during early times and midcycle by the transcription factor EUO, until this repression is relieved at late times by an as-yet-undefined mechanism (12,13).…”

Section: Discussionmentioning

confidence: 99%

“…Changes in DNA supercoiling during the chlamydial developmental cycle have been examined by measuring the superhelical density of the plasmid, which is a commonly used surrogate marker of chromosomal DNA supercoiling in bacteria (21). This approach has shown that chlamydial DNA supercoiling levels are the highest in midcycle, with lower levels being found early and late in the intracellular infection (7). This temporal pattern predicts that supercoilingdependent promoters have a low level of initial transcription that increases in midcycle and then decreases at late times, which is the transcriptional profile that we determined for supercoiling-dependent bioY P1 (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…To relax the plasmid DNA, 10 g of CsCl gradient-purified plasmid DNA was treated with wheat germ topoisomerase I (Promega) as previously described (7). DNA relaxation was verified by electrophoresis on a 1% agarose gel in 1ϫ TAE buffer (0.01 M Tris-acetate, 1 mM EDTA).…”

Section: Methodsmentioning

confidence: 99%

“…DNA supercoiling, which peaks in midcycle, is proposed to regulate genes with supercoilingresponsive promoters, which include midcycle genes and a subset of early genes (7,8). Late genes consist of two subsets that are transcribed by either the major chlamydial RNA polymerase, which contains the sigma factor 66 , or an alternative RNA polymerase containing 28 (7,(9)(10)(11). Both subsets of late genes, however, are negatively regulated by the same transcription factor, EUO, which appears to be the master regulator of late gene expression (12,13).…”

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confidence: 99%

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Regulation of Chlamydia Gene Expression by Tandem Promoters with Different Temporal Patterns

Rosario

Tan

2016

J Bacteriol

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Chlamydia is a genus of pathogenic bacteria with an unusual intracellular developmental cycle marked by temporal waves of gene expression. The three main temporal groups of chlamydial genes are proposed to be controlled by separate mechanisms of transcriptional regulation. However, we have noted genes with discrepancies, such as the early gene dnaK and the midcycle genes bioY and pgk, which have promoters controlled by the late transcriptional regulators EUO and 28 . To resolve this issue, we analyzed the promoters of these three genes in vitro and in Chlamydia trachomatis bacteria grown in cell culture. Transcripts from the 28 -dependent promoter of each gene were detected only at late times in the intracellular infection, bolstering the role of 28 RNA polymerase in late gene expression. In each case, however, expression prior to late times was due to a second promoter that was transcribed by 66 RNA polymerase, which is the major form of chlamydial polymerase. These results demonstrate that chlamydial genes can be transcribed from tandem promoters with different temporal profiles, leading to a composite expression pattern that differs from the expression profile of a single promoter. In addition, tandem promoters allow a gene to be regulated by multiple mechanisms of transcriptional regulation, such as DNA supercoiling or late regulation by EUO and 28 . We discuss how tandem promoters broaden the repertoire of temporal gene expression patterns in the chlamydial developmental cycle and can be used to fine-tune the expression of specific genes. IMPORTANCE Chlamydia is a pathogenic bacterium that is responsible for the majority of infectious disease cases reported to the CDC each year. It causes an intracellular infection that is characterized by coordinated expression of chlamydial genes in temporal waves.Chlamydial transcription has been shown to be regulated by DNA supercoiling, alternative forms of RNA polymerase, and transcription factors, but the number of transcription factors found in Chlamydia is far fewer than the number found in most bacteria. This report describes the use of tandem promoters that allow the temporal expression of a gene or operon to be controlled by more than one regulatory mechanism. This combinatorial strategy expands the range of expression patterns that are available to regulate chlamydial genes.A defining feature of the pathogenic bacterium Chlamydia is an unusual intracellular developmental cycle with three main stages (1). During the early stage, an extracellular form of chlamydiae, called the elementary body (EB), enters the host eukaryotic cell and differentiates into a reticulate body (RB), which is the metabolically active but noninfectious form. During the midstage, the RB replicates via multiple rounds of binary fission. Finally, in the late stage, RBs convert back into infectious EBs. This developmental cycle lasts 48 to 72 h and ends with the release of EBs to infect a new host cell. These fundamental steps of the developmental cycle are conserved among species of...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Regulation of Chlamydia Gene Expression by Tandem Promoters with Different Temporal Patterns

Rosario

Tan

2016

J Bacteriol

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One Face of Chlamydia trachomatis: The Infectious Elementary Body

Cossé

Hayward

Subtil

2016

Current Topics in Microbiology and Immunology

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The lifestyle of Chlamydiae is unique: the bacteria alternate between two morphologically distinct forms, an infectious non-replicative elementary body (EB), and a replicative, non-infectious reticulate body (RB). This review focuses on recent advances in understanding the structure and function of the infectious form of the best-studied member of the phylum, the human pathogen Chlamydia trachomatis. Once considered as an inert particle of little functional capacity, the EB is now perceived as a sophisticated entity that encounters at least three different environments during each infectious cycle. We review current knowledge on its composition and morphology, and emerging metabolic activities. These features confer resistance to the extracellular environment, the ability to penetrate a host cell and ultimately enable the EB to establish a niche enabling bacterial survival and growth. The bacterial and host molecules involved in these processes are beginning to emerge.

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The bacterial Tn9 chloramphenicol resistance gene: an attractive DNA segment for Mos1 mariner insertions

et al. 2008

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The eukaryotic mariner transposons are currently thought to have no sequence specificity for integration other than to insert within a TA contained in a degenerated [TA](1-4) tract, either in vitro or in vivo. We have investigated the properties of a suspected hotspot for the integration of the mariner Mos1 element, namely the Tn9 cat gene that encodes a chloramphenicol acetyl transferase. Using in vitro and bacterial transposition assays, we confirmed that the cat gene is a preferential target for MOS1 integration, whatever its sequence environment, copy number or chromosomal locus. We also observed that its presence increases transposition rates both in vitro and in bacterial assays. The structural and sequence features that constitute the attractiveness of cat were also investigated. We first demonstrated that supercoiling is essential for the cat gene to be a hot spot. In contrast to the situation for Tc1-like elements, DNA curvature and bendability were not found to affect integration target preferences. We found that Mos1 integrations do not occur randomly along the cat gene. All TA dinucleotides that are preferred for integration were found within either TATA or TA x TA motifs. However, these motifs are not sufficient to constitute an attractive dinucleotide, since four TATA and TA x TA sites are cold spots.

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DNA Supercoiling-Dependent Gene Regulation in Chlamydia

Cited by 36 publications

References 51 publications

Regulation of Chlamydia Gene Expression by Tandem Promoters with Different Temporal Patterns

Regulation of Chlamydia Gene Expression by Tandem Promoters with Different Temporal Patterns

One Face of Chlamydia trachomatis: The Infectious Elementary Body

The bacterial Tn9 chloramphenicol resistance gene: an attractive DNA segment for Mos1 mariner insertions

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