The excision proteins of CTnDOT positively regulate the transfer operon

Keeton, Carolyn M.; Park, Jiyeon; Wang, Gui Rong; Hopp, Crystal M.; Shoemaker, Nadja B.; Gardner, Jeffrey F.; Salyers, Abigail A.

doi:10.1016/j.plasmid.2012.12.001

Cited by 10 publications

(13 citation statements)

References 29 publications

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“…If transfer were to happen prematurely, an Hfr-like transfer would be the consequence, which could be rather costly to the donor cell. Many studies have detailed the coordinated regulation of excision and transfer of CTnDOT (10,13,14,24), while this report is the first to characterize the transcriptional regulation of CTnDOT mobilization functions.…”

Section: Discussionmentioning

confidence: 90%

“…A deletion of xis2c had no noticeable effect on the mob transcriptional activation. This was unexpected, as we predicted that a deletion of xis2c would greatly diminish mob activation based on the observation that xis2c is required for tra operon activation (13). Further, a deletion of exc had no effect on the tra operon and yet brought mob activation down to the constitutive levels in the absence of Tc.…”

Section: Figmentioning

confidence: 96%

“…After observing that the mob genes from CTnDOT are detected only upon exposure to Tc, we predicted that proteins encoded within the excision operon are acting as regulators of the mob operon. We have previously reported that when the excision operon is provided in trans with the self-transmissible plasmid pLYL72, there is transcriptional activation of the tra genes as well as enhanced pLYL72 transfer (9,11,13). Because of the close proximity of the tra promoter and the putative mob promoter, we predicted that the interactions that regulate the tra operon could also be mediating mob transcriptional activation.…”

Section: Figmentioning

confidence: 99%

“…Many studies have described transcriptional regulation of both excision and transfer of CTnDOT (10,11,13,14), but thus far we have yet to characterize a very important set of genes involved in CTnDOT conjugative transfer: the mobilization region. The CTnDOT mob genes encode proteins that are involved in formation of the relaxosome that is required to nick the oriT and for coupling the CTnDOT circular intermediate to the mating bridge (15).…”

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confidence: 99%

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Tetracycline-Related Transcriptional Regulation of the CTnDOT Mobilization Region

2013

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CTnDOT is a 65-kb conjugative transposon (CTn) in Bacteroides spp. that confers resistance to the antibiotics erythromycin and tetracycline (Tc). Conjugative transfer of CTnDOT is regulated upon exposure of cells to Tc. In the absence of Tc, no transfer is detectable; however, a cascade of regulatory events results in the conjugative transfer of CTnDOT upon Tc induction. Previous studies addressing regulation of CTnDOT conjugative transfer focused primarily on the 13-kb transfer (tra) operon, which encodes the proteins required for assembly of the mating apparatus. We report here that the mob operon that encodes the relaxase and coupling proteins required for mobilization of CTnDOT are regulated at the transcriptional level upon Tc induction. The Xis2d and Exc excision proteins are required for the upregulation of mob transcription upon Tc induction, and yet a deletion of xis2c has no effect. We also show preliminary evidence suggesting that the integrase, IntDOT, may play a regulatory role, as pLYL72 transfer is not detectable when intDOT is provided in trans.

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Section: Discussionmentioning

confidence: 90%

Section: Figmentioning

confidence: 96%

Section: Figmentioning

confidence: 99%

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confidence: 99%

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Tetracycline-Related Transcriptional Regulation of the CTnDOT Mobilization Region

2013

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“…All B. thetaiotaomicron cultures were grown anaerobically to an optical density at 650 nm (OD 650 ) of 0.8, as described previously (10). The cells in the cultures were then pelleted by centrifugation and frozen at Ϫ80°C.…”

Section: Media and Antibioticsmentioning

confidence: 99%

The Bacteroides thetaiotaomicron Protein Bacteroides Host Factor A Participates in Integration of the Integrative Conjugative Element CTnDOT into the Chromosome

Ringwald

Gardner

2015

J Bacteriol

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CTnDOT is a conjugative transposon found in Bacteroides species. It encodes multiple antibiotic resistances and is stimulated to transfer by exposure to tetracycline. CTnDOT integration into the host chromosome requires IntDOT and a previously unknown host factor. We have identified a protein, designated BHFa (Bacteroides host factor A), that participates in integrative recombination. BHFa is the first host factor identified for a site-specific recombination reaction in the CTnDOT family of integrative and conjugative elements. Based on the amino acid sequence of BHFa, the ability to bind specifically to 4 sites in the attDOT DNA, and its activity in the integration reaction, BHFa is a member of the IHF/HU family of nucleoid-associated proteins. Other DNA bending proteins that bind DNA nonspecifically can substitute for BHFa in the integration reaction. IMPORTANCEBacteroides species are normal members of the human colonic microbiota. These species can harbor and spread self-transmissible genetic elements (integrative conjugative elements [ICEs]) that contain antibiotic resistance genes. This work describes the role of a protein, BHFa, and its importance in the integration reaction required for the element CTnDOT to persist in Bacteroides host cells. Bacteroides species are Gram-negative, obligate anaerobes that are part of the normal microbiota in the human colon (1). When the gut is punctured, Bacteroides can act as an opportunistic pathogen that may form abscesses in other regions of the body. Treatment of the abscesses is complicated by widespread resistance to tetracycline and erythromycin carried by integrative conjugative elements (ICEs) (also called conjugative transposons [CTns]) found in Bacteroides. These elements are capable of transferring between diverse organisms by conjugation and integrate into the host bacterium's chromosome. Due to this integration, ICEs are maintained stably, even in the absence of selective pressure. As a result, the frequency of antibiotic resistance in Bacteroides has increased dramatically over the last 30 years (2). ICEs also carry genes to regulate and carry out their own transfer. Furthermore, some ICEs can mobilize coresident genetic elements that could not otherwise transfer (3). Because of their benefit to the bacterial host and their ability to transfer among organisms, ICEs are widespread in both Gram-positive and -negative bacterial populations (2).CTnDOT is a well-characterized ICE found in Bacteroides species. It carries the ermF and tetQ genes that encode resistance to erythromycin and tetracycline, respectively. Exposure to tetracycline induces the excision and transfer of CTnDOT. CTnDOT integration and excision require an integrase, IntDOT, and a hostencoded protein factor. IntDOT is a tyrosine recombinase and is in the same family of enzymes as Int, Flp, XerC, XerD, and Cre (4). IntDOT contains five of the six conserved amino acid residues that form the catalytic sites of tyrosine recombinases (5, 6). These enzymes perform strand exchanges by a site-...

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The Genus Bacteroides

Wexler

2014

The Prokaryotes

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The excision proteins of CTnDOT positively regulate the transfer operon

Cited by 10 publications

References 29 publications

Tetracycline-Related Transcriptional Regulation of the CTnDOT Mobilization Region

Tetracycline-Related Transcriptional Regulation of the CTnDOT Mobilization Region

The Bacteroides thetaiotaomicron Protein Bacteroides Host Factor A Participates in Integration of the Integrative Conjugative Element CTnDOT into the Chromosome

The Genus Bacteroides

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