<i>Bacteroides fragilis</i> mobilizable transposon Tn<i>5520</i> requires a 71 base pair origin of transfer sequence and a single mobilization protein for relaxosome formation during conjugation

Vedantam, Gayatri; Knopf, Sarah; Hecht, David W.

doi:10.1111/j.1365-2958.2005.04934.x

Cited by 14 publications

(17 citation statements)

References 65 publications

(93 reference statements)

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“…Previous studies had identified a Bacteroides consensus nick site with cleavage between adjacent guanine and cytosine residues (34,43). Site-directed mutations of potential cleavage sites allowed the identification of the CTn341 nick site within the 120-bp oriT region and showed that it was related to several other known Bacteroides nick sites.…”

Section: Discussionmentioning

confidence: 98%

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Genetic and Functional Analyses of the mob Operon on Conjugative Transposon CTn 341 from Bacteroides spp

2010

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Bacteroides are Gram-negative anaerobes indigenous to the intestinal tract of humans, and they are important opportunistic pathogens. Mobile genetic elements, such as conjugative transposons (CTns), have contributed to an increase in antibiotic resistance in these organisms. CTns are self-transmissible elements that belong to the superfamily of integrative and conjugative elements (ICEs). CTn341 is 52 kb; it encodes tetracycline resistance and its transfer is induced by tetracycline. The mobilization region of CTn341 was shown to be comprised of a three-gene operon, mobABC, and the transfer origin, oriT. The three genes code for a nicking accessory protein, a relaxase, and a VirD4-like coupling protein, respectively. The Mob proteins were predicted to mediate the formation of the relaxosome complex, nick DNA at the oriT, and shuttle the DNA/protein complex to the mating-pore apparatus. The results of mutational studies indicated that the three genes are required for maximal transfer of CTn341. Mob gene transcription was induced by tetracycline, and this regulation was mediated through the two-component regulatory system, RteAB. The oriT region of CTn341 was located within 100 bp of mobA, and a putative Bacteroides consensus nicking site was observed within this region. Mutation of the putative nick site resulted in a loss of transfer. This study demonstrated a role of the mobilization region for transfer of Bacteroides CTns and that tetracycline induction occurs for the mob gene operon, as for the tra gene operon(s), as shown previously.

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Section: Discussionmentioning

confidence: 98%

“…Previously, consensus nick sites were determined for several Bacteroides-transmissible elements, and these were found to cleave between guanine and cytosine residues (34,43). Using a pattern-matching homology search, we examined the 120-bp Quantitative RT-PCR analysis of the mobA, mobB, and traA genes in rteA and rteB mutants.…”

Section: Resultsmentioning

confidence: 99%

Genetic and Functional Analyses of the mob Operon on Conjugative Transposon CTn 341 from Bacteroides spp

2010

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“…In contrast to those of conjugative plasmids, origins of transfer and the cognate relaxases from only a few ICEs have been identified and characterized (1,12,56,62). Where characterized, oriT on an ICE is required in cis for transfer but usually not for excision, although there are possible exceptions (60).…”

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confidence: 99%

“…The DNA relaxase terminates transfer by precisely rejoining the ends of the plasmid and releasing a single-stranded DNA circle into the recipient (37, 48). Synthesis of the complementary strand of the transferred circle initiates primarily at an origin of plasmid replication (53).In contrast to those of conjugative plasmids, origins of transfer and the cognate relaxases from only a few ICEs have been identified and characterized (1,12,56,62). Where characterized, oriT on an ICE is required in cis for transfer but usually not for excision, although there are possible exceptions (60).…”

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confidence: 99%

Identification of the Origin of Transfer ( oriT ) and DNA Relaxase Required for Conjugation of the Integrative and Conjugative Element ICE Bs1 of Bacillus subtilis

2007

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Integrative and conjugative elements (ICEs), also known as conjugative transposons, are mobile genetic elements that can transfer from one bacterial cell to another by conjugation. ICEBs1 is integrated into the trnS-leu2 gene of Bacillus subtilis and is regulated by the SOS response and the RapI-PhrI cell-cell peptide signaling system. When B. subtilis senses DNA damage or high concentrations of potential mating partners that lack the element, ICEBs1 excises from the chromosome and can transfer to recipients. Bacterial conjugation usually requires a DNA relaxase that nicks an origin of transfer (oriT) on the conjugative element and initiates the 5-to-3 transfer of one strand of the element into recipient cells. The ICEBs1 ydcR (nicK) gene product is homologous to the pT181 family of plasmid DNA relaxases. We found that transfer of ICEBs1 requires nicK and identified a cis-acting oriT that is also required for transfer. Expression of nicK leads to nicking of ICEBs1 between a GC-rich inverted repeat in oriT, and NicK was the only ICEBs1 gene product needed for nicking. NicK likely mediates conjugation of ICEBs1 by nicking at oriT and facilitating the translocation of a single strand of ICEBs1 DNA through a transmembrane conjugation pore.Mobile genetic elements are ubiquitous in bacteria and can contain genes for antibiotic resistance, symbiosis, and virulence; their dissemination contributes to bacterial evolution by conferring new genes and phenotypes to their recipients (reviewed in references 8 and 21). The most common mobile genetic elements are phages, plasmids, and integrative and conjugative elements (ICEs), also known as conjugative transposons. Conjugative plasmids and ICEs are transferred directly from cell to cell and generally encode their own conjugation systems (6,25).ICEBs1 is an ICE that is found integrated into the trnS-leu2 genes of some Bacillus subtilis strains (Fig. 1A) (3, 7). Detailed analyses of ICEBs1 have been aided by its efficient transfer, its site-specific integration, and the ease of genetic manipulations in B. subtilis (2, 3; C. A. Lee, J. M. Auchtung, R. E. Monson, and A. D. Grossman, submitted for publication). When induced, ICEBs1 excises from the chromosome and can transfer to recipient cells. ICEBs1 gene expression and excision are induced by the SOS response or when cells are at high density surrounded by neighbors that do not contain a copy of ICEBs1 (3). Regulation by population density and recognition of self are mediated by the regulator RapI and the pentapeptide PhrI (3).Both DNA damage and RapI-PhrI regulation affect the activity of the ICEBs1 immunity repressor ImmR (2), and inactivation of ImmR causes increased ICEBs1 gene expression, production of the excisionase Xis, and excision of ICEBs1 (2, 3; Lee et al., submitted). Integration into and excision from the chromosome by site-specific recombination is mediated by a lambda-like integrase, Int, encoded in ICEBs1 (Lee et al., submitted). Excision requires both Xis and Int, whereas integration requires only Int (Lee et ...

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“…Interestingly, we also observed linearization of plasmid upon incubation with even the lowest concentration of Tfs4 VirD2. Cleavage of both DNA strands may reflect nonspecific activity, as similarly observed for the BmpH Mob protein of the Tn 5520 mobilizable transposon (54) and for the Orf20 relaxase of the conjugative transposon Tn 916 when incubated with DNA in the absence of an auxiliary specificity protein (24). A similar requirement may contribute to the residual in vitro activity of Tfs4 VirD2 seen here.…”

Section: Discussionmentioning

confidence: 86%

Site-specific Relaxase Activity of a VirD2-like Protein Encoded within the tfs4 Genomic Island of Helicobacter pylori

Grove

Alandiyjany

Delahay

2013

Journal of Biological Chemistry

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Background: The complement of factors involved in mobilization of the Helicobacter pylori disease-associated tfs4 genomic island are presently unknown.Results: tfs4 encodes a VirD2-like relaxase with distinctive DNA binding and nicking activity.Conclusion: Tfs4 VirD2 probably initiates mobilization of tfs4 by specific interaction at a chromosomal transfer origin sequence.Significance: Tfs4 VirD2-mediated mobilization of tfs4 may increase pathogenic potential of H. pylori strains.

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Bacteroides fragilis mobilizable transposon Tn5520 requires a 71 base pair origin of transfer sequence and a single mobilization protein for relaxosome formation during conjugation

Cited by 14 publications

References 65 publications

Genetic and Functional Analyses of the mob Operon on Conjugative Transposon CTn 341 from Bacteroides spp

Genetic and Functional Analyses of the mob Operon on Conjugative Transposon CTn 341 from Bacteroides spp

Identification of the Origin of Transfer ( oriT ) and DNA Relaxase Required for Conjugation of the Integrative and Conjugative Element ICE Bs1 of Bacillus subtilis

Site-specific Relaxase Activity of a VirD2-like Protein Encoded within the tfs4 Genomic Island of Helicobacter pylori

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