Molecular characterization of two proteins involved in the excision of the conjugative transposon Tn1545: homologies with other site-specific recombinases.

Poyart-Salmeron, C.; Trieu‐Cuot, Patrick; Carlier, C; Courvalin, Patrice

doi:10.1002/j.1460-2075.1989.tb08373.x

Cited by 144 publications

(143 citation statements)

References 62 publications

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“…We have never detected virions that appear to have arisen from site specific recombination between the ERs flanking the prophage, a process that could theoretically also result in excision of prophage DNA. Many mobile genetic elements, including lambdoid phages, phage P2, and Tn916, use such a process to generate extrachromosomal forms of DNA (9,17). However, these elements depend on an element-encoded excisionase (e.g., Xis) to reverse the integration pathway, and such a protein is not known to be encoded within CTX .…”

Section: Discussionmentioning

confidence: 99%

CTXφ contains a hybrid genome derived from tandemly integrated elements

Davis

Waldor

2000

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

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CTX is a filamentous, temperate bacteriophage whose genome includes ctxAB, the genes that encode cholera toxin. In toxigenic isolates of Vibrio cholerae, tandem arrays of prophage DNA, usually interspersed with the related genetic element RS1, are integrated site-specifically within the chromosome. We have discovered that these arrays routinely yield hybrid virions, composed of DNA from two adjacent prophages or from a prophage and a downstream RS1. Coding sequences are always derived from the 5 prophage whereas most of an intergenic sequence, intergenic region 1, is always derived from the 3 element. The presence of tandem elements is required for production of virions: V. cholerae strains that contain a solitary prophage rarely yield CTX virions, and the few virions detected result from imprecise excision of prophage DNA. Thus, generation of the replicative form of CTX , pCTX, a step that precedes production of virions, does not depend on reversal of the process for site-specific integration of CTX DNA into the V. cholerae chromosome. Production of pCTX also does not depend on RecA-mediated homologous recombination between adjacent prophages. We hypothesize that the CTX -specific proteins required for replication of pCTX can also function on a chromosomal substrate, and that, unlike the processes used by other integrating phages, production of pCTX and CTX does not require excision of the prophage from the chromosome. Use of this replication strategy maximizes vertical transmission of prophage DNA while still enabling dissemination of CTX to new hosts. C TX is a filamentous phage whose single-stranded DNA genome includes ctxAB, the genes that encode cholera toxin (CT) (1), the primary virulence factor produced by the choleragenic bacterium Vibrio cholerae (2). Unlike the filamentous phages that infect Escherichia coli, CTX can give rise to lysogens, which contain the phage genome integrated into the bacterial chromosome (1, 3, 4). Integration of CTX DNA into the V. cholerae chromosome is a site-specific process that does not require RecA (5). Both O1 El Tor and O139 strains of V. cholerae, which have caused virtually all recent cholera epidemics, have just one chromosomal locus within which the phage genome is integrated (3, 6). The core of this integration site (attB) is a 17-bp sequence that is almost identical to an 18-bp sequence within the phage genome. Integration of phage DNA into the genome of an attB ϩ , CTX Ϫ El Tor strain of V. cholerae yields single or tandem prophages flanked by these 17͞18-bp sequences, which are known as end repeats (ERs) (5). If such a lysogen is infected by an additional phage or transformed with the replicative form (RF) (a plasmid) of phage DNA, the new phage DNA will integrate at an ER between tandem prophages or between a 3Ј end and chromosomal DNA; the ER between the 5Ј end of a prophage and adjacent chromosomal DNA is not used (7).Toxigenic strains of V. cholerae frequently also contain a genetic element related to CTX , known as RS1 (4). This element is found on the chr...

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Section: Discussionmentioning

confidence: 99%

CTXφ contains a hybrid genome derived from tandemly integrated elements

Davis

Waldor

2000

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

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“…The DNA fragments to be used as probes for hybridization experiments were the 870-bp HincIl fragment of pT181 for tet(K) (15), the 310-bp ClaI-HpaII fragment of pBC16 for tet(L) (13), the 850-bp ClaI-HindIII fragment of TnJS45 for tet(M) (18), the 1,458-bp HindIII-NdeI fragment of pIP1433 for tet(O) (32), the 900-bp SphI-EcoRI fragment of pCW3 for tetA(P) (31), the 1,100-bp PstI-EcoRI fragment of pCW3 for tetB(P) (31), the 900-bp EcoRI-EcoRV fragment of pNFD13-2 for tet(Q) (20), the 590-bp fragment of pIP811 for tet(S) (5), and the 830-bp TaqI fragment of Tn1545 for int-Tn (23). Restriction endonuclease-generated fragments were separated by electrophoresis in 0.8% low-melting-temperature agarose type VII (Sigma Chemical Co., St. Louis, Mo.)…”

Section: Methodsmentioning

confidence: 99%

“…The distributions of tet(M) and tet(O) among gram-positive bacteria differed: the tet(M) gene was found, alone or associated with other tet genes, in all of the nine streptococcal isolates and in 219 (96%) of the enterococcal isolates analyzed, whereas tet(O) was detected associated with other tet genes in single isolates of E. faecalis and of S. milleri. The tet(M) gene is common among enterococci and streptococci, where it is part of broad-host-range conjugative transposons and is thus usually associated with int-Tn, the gene encoding the integrase of these elements (23,24). In contrast, tet(O) is rarely encountered in these genera, where it is carried by conjugative plasmids (33,35,37) (19).…”

Section: Methodsmentioning

confidence: 99%

Presence of the Listeria tetracycline resistance gene tet(S) in Enterococcus faecalis

Charpentier

Gerbaud

Courvalin

1994

Antimicrob Agents Chemother

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Two hundred thirty-eight tetracycline-and minocycline-resistant clinical isolates of Enterococcus and Streptococcus spp. were investigated by dot blot hybridization for the presence of nucleotide sequences related to tet(S) (first detected in Listeria monocytogenes BM4210), tet(K), tet(L), tet(M), tet(O), tet(P), and tet(Q) genes. The tet(S) determinant was found in 22 strains of Enterococcus faecalis, associated with tet(M) in 9 of these isolates and further associated with tet(L) in 3 of these strains. tet (M)

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“…Thus, the molecular mechanisms proposed for movement of transposons cannot apply to the conjugative elements; lambda and other prophages provide a better model for their movement (12,13). The recent finding that the TnJ545 gene required for excision of this element has homology with the lambda integrase family of proteins supports this idea (21).…”

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confidence: 91%

The presence of conjugative transposon Tn916 in the recipient strain does not impede transfer of a second copy of the element

Norgren

Scott

1991

J Bacteriol

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Transfer of the conjugative transposon Tn916 from the chromosome of Bacillus subtilis to a transposon-free Streptococcus pyogenes strain occurs at the same frequency as transfer to a Tn916-containing recipient. This rules out a model for conjugal transfer of Tn916 in which a copy of the element in the recipient represses transposition of a copy introduced by conjugation. Homology-directed integration of the incoming transposon into the resident one is less frequent than insertion elsewhere in the chromosome. This shows that after conjugation, transposition occurs more frequently than homologous recombination. However, because transconjugants arising from homologous recombination can be selected, it is possible to use Tn916 as a shuttle for gram-positive organisms for which there is no easy means of introducing DNA.

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Molecular characterization of two proteins involved in the excision of the conjugative transposon Tn1545: homologies with other site-specific recombinases.

Cited by 144 publications

References 62 publications

CTXφ contains a hybrid genome derived from tandemly integrated elements

CTXφ contains a hybrid genome derived from tandemly integrated elements

Presence of the Listeria tetracycline resistance gene tet(S) in Enterococcus faecalis

The presence of conjugative transposon Tn916 in the recipient strain does not impede transfer of a second copy of the element

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