Enterobacteriaceae plasmids enhancing chemical mutagenesis and their distribution among incompatibility groups

Molina, A. M.; Babudri, Nora; Tamaro, M.; Venturini, S.; Monti‐Bragadin, C.

doi:10.1111/j.1574-6968.1979.tb03241.x

Cited by 37 publications

(12 citation statements)

References 28 publications

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“…Finally, it should be noted that the high level of mutagenesis promoted by the cloned rumAB (R391) operon is in stark contrast to the limited ability of the native R391 plasmid to promote mutagenesis functions (8,27,28,39,53). One obvious explanation for this difference is that the UV sensitization gene(s) carried by R391 (and other IncJ plasmids) (35,39,53) masks the inherent ability of rumAB (R391) to exhibit mutagenic DNA repair.…”

Section: Discussionmentioning

confidence: 60%

“…These so-called mutagenesis proteins can be expressed chromosomally, like the UmuDC proteins from Escherichia coli and Salmonella typhimurium (19,37,48,52), or episomally from certain naturally occurring plasmids (23,31,37,38). Indeed, R plasmids from over 10 different incompatibility groups can restore or increase the mutation frequency in a variety of E. coli strains, suggesting that they carry functionally active Umu homologs (8,27,28,39,53).…”

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confidence: 99%

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Characterization of the umu-complementing operon from R391

et al. 1995

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In addition to conferring resistances to antibiotics and heavy metals, certain R factors carry genes involved in mutagenic DNA repair. These plasmid-encoded genes are structurally and functionally related to the chromosomally encoded umuDC genes of Escherichia coli and Salmonella typhimurium. Three such plasmid operons, mucAB, impCAB, and samAB, have been characterized at the molecular level. Recently, we have identified three additional umu-complementing operons from IncJ plasmid R391 and IncL/M plasmids R446b and R471a. We report here the molecular characterization of the R391 umu-complementing operon. The nucleotide sequence of the minimal R plasmid umu-complementing (rum) region revealed an operon of two genes, rumA (R391) and rumB (R391) , with an upstream regulatory signal strongly resembling LexA-binding sites. Phylogenetic analysis revealed that the RumAB (R391) proteins are approximately equally diverged in sequence from the chromosomal UmuDC proteins and the other plasmid-encoded Umu-like proteins and represent a new subfamily. Genetic characterization of the rumAB (R391) operon revealed that in recA ؉ and recA1730 backgrounds, the rumAB (R391) operon was phenotypically indistinguishable from mucAB. In contrast, however, the rumAB (R391) operon gave levels of mutagenesis that were intermediate between those given by mucAB and umuDC in a recA430 strain. The latter phenotype was shown to correlate with the reduced posttranslational processing of the RumA (R391) protein to its mutagenically active form, RumA (R391) . Thus, the rumAB (R391) operon appears to possess characteristics that are reminiscent of both chromosome and plasmid-encoded umu-like operons.

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Section: Discussionmentioning

confidence: 60%

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confidence: 99%

Characterization of the umu-complementing operon from R391

et al. 1995

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“…umu genes that analogous operons exist on many conjugative plasmids (10,22,23,32,39,48,50). Two such operons, mucAB and impCAB, have been cloned from plasmids pKM101 and TP110, respectively (10,31).…”

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“…The two umu genes encode an uncharacterized activity which increases the ability of the cell to tolerate and repair damage at the expense of genetic fidelity (8,15,47). It is an interesting evolutionary feature of umu genes that analogous operons exist on many conjugative plasmids (10,22,23,32,39,48,50). Two such operons, mucAB and impCAB, have been cloned from plasmids pKM101 and TP110, respectively (10, 31).…”

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Structural characterization of the Salmonella typhimurium LT2 umu operon

Thomas¹,

Crowne²,

Pidsley³

et al. 1990

J Bacteriol

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The umuDC operon of Escherichia coli encodes functions required for mutagenesis induced by radiation and a wide variety of chemicals. The closely related organism Salmonella typhimurium is markedly less mutable than E. coli, but a umu homolog has recently been identffied and cloned from the LT2 subline. In this study the nucleotide sequence and structure of the S. typhimurium LT2 umu operon have been determined and its gene products have been identified so that the molecular basis of umu activity might be understood more fully. S. typhimurium LT2 umu consists of a smaller 417-base-pair (bp) umuD gene ending 2 bp upstream of a larger 1,266-bp umuC gene. The only apparent structural difference between the two operons is the lack of gene overlap. An SOS box identical to that found in E. coil is present in the promoter region upstream of umuD. The calculated molecular masses of the umuD and umuC gene products were 15.3 and 47.8 kilodaltons, respectively, which agree with figures determined by transpositional disruption and maxicell analysis. The S. typhimurium and E. coli umuD sequences were 68% homologous and encoded products with 71% amino acid identity; the umuC sequences were 71% homologous and encoded products with 83% amino acid identity. Furthermore, the potential UmuD cleavage site and associated catalytic sites could be identified. Thus the very different mutagenic responses of S. typhimurium LT2 and E. coli cannot be accounted for by gross differences in operon structure or gene products. Rather, the ability of the cloned S. typhimurium umuD gene to give stronger complementation of E. coli umuD77 mutants in the absence of a functional umuC gene suggests that Salmonella UmuC protein normally constrains UmuD protein activity.Activity of the umuDC operon of Escherichia coli is essential for mutagenesis induced by a variety of physical and chemical agents (38,52,55). The two umu genes encode an uncharacterized activity which increases the ability of the cell to tolerate and repair damage at the expense of genetic fidelity (8,15,47). It is an interesting evolutionary feature of umu genes that analogous operons exist on many conjugative plasmids (10,22,23,32,39,48,50). Two such operons, mucAB and impCAB, have been cloned from plasmids pKM101 and TP110, respectively (10, 31).Expression of umuDC, mucAB, and impCAB genes is under the control of the SOS response (1, 6-8, 41). Under normal cellular conditions, transcription of these genes is repressed by the presence of LexA protein bound to a consensus binding sequence in the operator region of each operon (52). When DNA damage occurs, LexA repressor undergoes autoproteolytic cleavage by interaction with a complex of RecA protein, single-stranded DNA, and ATP (17, 43), and transcription of SOS-inducible genes ensues. However, for full mutagenic repair activity, the UmuD protein of E. coli or the MucA protein must itself be cleaved by interaction with the same "activated" RecA protein complex (3,9,21,25,40). The autoproteolytic cleavage of LexA, UmuD, and MucA protei...

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“…The umuD and umuC genes are organized as an operon (11,47) and encode proteins of 15.1 and 47.7 kDa, respectively (20,38). Operons analogous to umuDC have been found in many conjugative plasmids (33,40,54). Two such operons, mucAB and impAB, have been cloned from plasmids pKM101 and TP110, respectively, and have been shown to encode proteins with molecular weights similar to those of the umuDC products (14,38).…”

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Salmonella typhimurium has two homologous but different umuDC operons: cloning of a new umuDC-like operon (samAB) present in a 60-megadalton cryptic plasmid of S. typhimurium

et al. 1991

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Expression of the umuDC operon is required for UV and most chemical mutagenesis in Escherichia coli. The DNA which can restore UV mutability to a umuD44 strain and to a umuC122::Tn5 strain of E. coli has been cloned from Salmonella typhimurium TA1538. DNA sequence analysis indicated that the cloned DNA potentially encoded proteins with calculated molecular weights of 15,523 and 47,726 and was an analog of the E. coli umuDC operon. We have termed this cloned DNA the samAB (for Salmonella mutagenesis) operon and tentatively referred to the umuDC operon of S. typhimurium LT2 (C. M. Smith, W. H. Koch, S. B. Franklin, P. L. Foster, T. A. Cebula, and E. Eisenstadt, J. Bacteriol. 172:4964-4978, 1990; S. M. Thomas, H. M.Crowne, S. C. Pidsley, and S. G. Sedgwick, J. Bacteriol. 172:4979-4987, 1990) as the umuDCST operon. The samAB operon is 40% diverged from the umuDCST operon at the nucleotide level. Among five umuDC-like operons so far sequenced, i.e., the samAB, umuDCST, mucAB, impAB, and E. coli umuDC operons, the samAB operon shows the highest similarity to the impAB operon of TP110 plasmid while the umuDCST operon shows the highest similarity to the E. coli umuDC operon. Southern hybridization experiments indicated that (i) S. typhimurium LT2 and TA1538 had both the samAB and the umuDCST operons and (ii) the samAB operon was located in a 60-MDa cryptic plasmid. The umuDCsT operon is present in the chromosome. The presence of the two homologous but different umuDC operons may be involved in the poor mutability of S. typhimurium by UV and chemical mutagens.

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Enterobacteriaceae plasmids enhancing chemical mutagenesis and their distribution among incompatibility groups

Cited by 37 publications

References 28 publications

Characterization of the umu-complementing operon from R391

Characterization of the umu-complementing operon from R391

Structural characterization of the Salmonella typhimurium LT2 umu operon

Salmonella typhimurium has two homologous but different umuDC operons: cloning of a new umuDC-like operon (samAB) present in a 60-megadalton cryptic plasmid of S. typhimurium

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