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R J Pinney

Publications and source records attributed to R J Pinney.

At least 37 records · Page 2Linked to original sources
PubMed1991

Plasmid pGW16, a derivative of pKM101, increases post-UV DNA synthesis, but sensitises some strains of Escherichia coli to UV.

Plasmid pKM101, which carries muc genes that are analogous in function to chromosomal umu genes, protected Escherichia coli strains AB1157 uvrB+ umuC+, JC3890 uvrB umuC+, TK702 uvrB+ umuC and TK501 uvrB umuC against ultraviolet irradiation (UV). Plasmid pGW16, a derivative of pKM101 selected for its increased spontaneous mutator effect, also gave some protection to the UmuC-deficient strains, TK702 and TK501. However, it sensitised the wild-type strain AB1157 to low, but protected against high doses of UV, whilst sensitising strain JC3890 to all UV doses tested. Even though its UV-protecting effects varied, pGW16 was shown to increase both spontaneous and UV-induced mutation in all strains. Another derivative of pKM101, plasmid pGW12, was shown to have lost all spontaneous and UV-induced mutator effects and did not affect post-UV survival. Plasmids pKM101 and pGW16 increased post-UV DNA synthesis in strains AB1157 and TK702, whereas pGW12 had no effect. Similarly, the wild-type UV-protecting plasmids R46, R446b and R124 increased post-UV DNA synthesis in strain TK501, but the non-UV-protecting plasmids R1, RP4 and R6K had no effect. These results accord with the model for error-prone DNA repair that requires umu or muc gene products for chain elongation after base insertion opposite non-coding lesions. They also suggest that the UV-sensitizing effects of pGW16 on umu+ strains can be explained in terms of overactive DNA repair resulting in lethal, rather than repaired UV-induced lesions.

Chromosomes, Bacterial↗
PubMed1991

Methicillin-resistant Staphylococcus aureus--an overview.

Methicillin-resistant strains of Staphylococcus aureus (MRSA) cause life-threatening infections, but they are no more pathogenic than methicillin-sensitive strains. Difficulties occur because of incorrect or missed identification of MRSA, and hence inappropriate or ineffective treatment of infections. Therapeutic options are severely limited and the increasing spectrum of resistance in MRSA is worrying. However, new methods of detection and new agents for treatment are being developed in response to the challenge of MRSA. Whilst the organism is a problem and control measures are necessary to contain its spread, the outlook is not bleak. In the medium term, the development of new, effective anti-MRSA agents should prevent the threat of MRSA becoming any greater in the field of hospital infection control.

Humans↗
PubMed1989

Studies of error-prone DNA repair in Escherichia coli K-12 and Ames Salmonella typhimurium strains using a model alkylating agent.

4-Acetoxy-3-acetoxymethyl acetophenone (AAMAP) is mutagenic in Ames Salmonella typhimurium tester strains TA100 and TA98, which carry plasmid pKM101, but not in the isogenic plasmid-less strains TA1535 and TA1538. Similarly, no AAMAP-induced reversion of the his-4 allele is detectable in Escherichia coli K-12 umuC strains in the absence of the plasmid, even when the strains are treated with ethylene-diaminetetraacetate to increase permeability, or when the uvrB allele is introduced to increase error-prone DNA repair. AAMAP is, however, mutagenic in umuC+ strains or in umuC strains in which plasmid pKM101 has been introduced, suggesting that the plasmid-encoded MucAB or the chromosomally determined UmuDC proteins are required for mutagenesis. Mutation frequencies are higher in E. coli umuC (pKM101) strains, which resemble Ames tester strains of S. typhimurium, than in E. coli umuC+ or even umuC+ (pKM101) strains. Therefore, providing that the recommended pKM101-containing tester strains are used, the apparent absence of Umu-like protein activity in S. typhimurium may actually increase the sensitivity of the Ames test for the detection of mutagens that require error-prone DNA repair for activity.

Acetophenones↗
PubMed1989

Relevance of plasmid pKM101-mediated mutagenicity in bacteria to genotoxicity in mammalian cells.

Three structurally related compounds, 4-acetoxy-3-acetoxy-methyl-acetophenone (AAMAP), 1-[4'-hydroxy-3'-hydroxy-methylphenyl]-2-[benzyl-t-butylamino] ethanone hydrochloride (HHBEH) and 1-[4'-hydroxy-3'-hydroxymethyl-phenyl]-2-[benzyl-t-butylamino] ethanol (HHBE), gave positive dose-related mutagenic responses in the Ames test when Salmonella typhimurium strain TA100 was used as the test organism. Strain TA100 carries the hisG46 allele, which is revertable by base changes, together with plasmid pKM101, which encodes mucAB genes that are analogous to umuDC, the chromosomal SOS-repair genes of Escherichia coli K-12. None of the compounds was mutagenic in Ames strain TA1535, which is the plasmid-free derivative of strain TA100. Only AAMAP, and that at only the highest concentration tested, was mutagenic in strain TA98, which detects frameshift mutations and carries plasmid pKM101. No compound was significantly mutagenic in strain TA1538, which is the plasmid-free derivative of strain TA98. When the three compounds were tested for the induction of sister-chromatid exchanges (SCEs) in Chinese hamster cells, the two more potent mutagens, AAMAP and HHBEH were found to increase SCEs, whereas HHBE did not give a significant response at any concentration tested. Ames test data showing plasmid pK101-dependent mutagenesis are therefore, at least for these compounds, relevant indicators of eukaryotic genotoxicity.

Animals↗
PubMed1985

Elimination of multicopy plasmid R6K by bleomycin.

Bleomycin eliminated multicopy plasmid R6K from growing cells of Escherichia coli AB1157 but failed to cure either of the low-copy plasmids R1 or R46. Measurements of R6K-encoded beta-lactamase and of covalently closed plasmid DNA indicated that the drug causes a progressive reduction in plasmid copy number.

Bleomycin↗
PubMed1984

Comparison of the Escherichia coli umu+-encoded function with plasmid R46-mediated error-prone repair in DNA-damaged cells.

Escherichia coli strain TK701 umu+ was more resistant than strain TK702 umu when tested against bleomycin (BLM), cis-platinum(II) diamminodichloride (PDD), ultraviolet light and methyl methanesulphonate (MMS), which produce single-strand DNA damage. However, the umu mutant was no more sensitive to mitomycin C (MTC) or proflavine (PF), which cause double-strand DNA binding. Strain TK702 umu was nonmutable by any of the agents, whereas mutations were induced in the wild-type strain by PDD, UV, MMS and MTC. The E. coli umu+ function therefore mimics plasmid R46-mediated error-prone repair in protecting only against single-strand DNA damage, whilst enhancing mutagenesis by both single- and double-strand damaging agents. Comparison of plasmid R46-mediated protection and mutagenesis in umu+ and umu strains indicated that the plasmid confers a greater error-prone DNA-repair activity in the mutant. Results are discussed in terms of analogy between host umu+ and plasmid muc+ functions.

DNA Repair↗
PubMed1984

Inhibition of bacterial DNA cytosine-5-methyltransferase by S-adenosyl-L-homocysteine and some related compounds.

S-Adenosyl-L-homocysteine and five related compounds have been evaluated as inhibitors of a DNA cytosine-5-methyltransferase. DNA methylation was assayed in cell extracts from E. coli strain J6-2 dcm+, proficient in DNA cytosine-5-methyltransferase activity, containing substrate DNA isolated from E. coli strain J6-2 dcm-, a strain deficient in DNA cytosine-5-methyltransferase. S-Adenosyl-L-homocysteine and its 7-deaza analogue, S-tubercidinylhomocysteine, were competitive inhibitors of DNA cytosine-5-methyltransferase with Ki's of 14.2 and 17.6 microM, respectively, in the above enzyme assay.

DNA (Cytosine-5-)-Methyltransferases↗
PubMed1983

Plasmid R46 fails to protect Escherichia coli against double-strand DNA-binding agents but increases their mutagenic activities.

Plasmid R46 was tested for its ability to increase survival and mutagenesis of Escherichia coli strain AB1157 following exposure to agents that produce a variety of structural defects in DNA. The plasmid enhanced the mutagenic activities of adriamycin (ADM), N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU), bleomycin (BLM), methyl methanesulphonate (MMS), mitomycin C (MTC), nitrofurazone (NFZ), 4-nitroquinoline-N-oxide (NQO), cis-platinum (II) diaminodichloride (PDD) and proflavine (PF). Furthermore, R46, which is known to protect against BLM and MMS, increased the survival of strain AB1157 following exposure to NFZ, NQO or PDD but not ADM, BCNU, MTC or PF. In fact the plasmid appeared to slightly sensitise its host to the latter drugs. The results are discussed in terms of the nature of the DNA damage produced by these inhibitors and the possible role of plasmid-encoded products in the repair of DNA.

Antineoplastic Agents↗
PubMed1983

Expression of eight unrelated Muc+ plasmids in eleven DNA repair-deficient E. coli strains.

23 plasmids from different incompatibility groups were tested for their ability to increase post-UV survival and UV-induced reversion to Arg+ in Escherichia coli strain AB1157 argE3 8 plasmids increased mutagenesis, of which 7 increased UV resistance. The exception, plasmid R391, sensitized AB1157 to UV. All 8 plasmids were absolutely dependent upon host recA+ and lexA+ genotypes for expression of these functions, but were independent of uvrA+, uvrB+, umuC+, recF+, polA+, uvrD+ or recL+. E. coli KMBL91 uvrE was sensitized to UV by R391, but protected by only 3 plasmids. All 8 plasmids restored mutation frequency in the non-mutable TK501 uvrB umuC strain to levels found in the JC3890 uvrB umuC+ parent strain. R391 sensitized TK501 to UV, but all other plasmids increased survival in the strain by over 1000-fold to levels found in the JC3890 uvrB umuC+ R+ strains. Plasmid R391 reduced the UV-protecting effect of R46 when both were present in strain TK501. Mutation frequencies were higher in TK501 (R46) than in TK501 (R391); in TK501 (R46/R391) they were slightly lower than in TK501 (R46).

Bacterial Proteins↗
PubMed1982

Plasmid R46-mediated protection against bleomycin is poLA+-dependent.

Strains of Escherichia coli deficient in post-replication recombination repair were more sensitive to bleomycin than wild-type, repair-proficient strains. Mutants lacking excision repair functions were no more sensitive to bleomycin than the wild-type strains, indicating that this pathway is not involved in the repair of bleomycin-damaged DNA. Plasmid R46 not only protected repair-proficient strains but also those with recB, recC, uvrA or lig genotypes, suggesting that R46 protection against bleomycin is independent of these host repair functions. However, R46 protection was abolished in recA or polA strains, indicating that these gene functions are necessary for plasmid-mediated protection. It is suggested that protection may be due to a recA+-dependent interaction of a plasmid-encoded product with host DNA polymerase I, resulting in an increase in the DNA repair capacity of cells.

Bleomycin↗
PubMed1981

Absence of ultraviolet-inducible DNA polymerase I-like activity in Escherichia coli strains harbouring R plasmids.

No DNA polymerase I-like activity was found associated with the ultraviolet (u.v.)-protecting plasmids R205, R46 or pKM101 in either uninduced or u.v.-induced wild-type or DNA polymerase I-deficient strains of Escherichia coli. Nor was any plasmid-associated polymerase activity detectable in similar systems containing u.v.-irradiated DNA as template. However, plasmids R205, R46 and pKM101 still increased survival and mutagenesis of the polymerase I-deficient E. coli strain after u.v. irradiation.

DNA Polymerase I↗
PubMed1978

Survival of plasmid-containing strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus in phenylmercuric nitrate and thiomersal.

Strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus harbouring plasmids that confer mercury resistance grew in nutrient broth containing concentrations of phenylmercuric nitrate (PMN) that were inhibitory to isogenic plasmid-less strains. Decimal reduction times of P. aeruginosa and S. aureus in aqueous PMN solution were also increased by the presence of plasmids. The viable count of a plasmid-containing P. aeruginosa strain in Davis and Mingioli's minimal medium (DM) containing 10 microgram ml-1 PMN fell by approximately 99% after 5 h. The count then remained constant for two weeks, when growth recommenced. This pattern of death followed by growth was also observed with the P. aeruginosa strain in DM + 10 microgram ml-1 thiomersal.

Culture Media↗
PubMed1978

Curing of an R factor from Escherichia coli by hydroxyurea and cytosine arabinoside.

Hydroxyurea (HU) and cytosine arabinoside (Ara-C) eliminate R factor R46 from Escherichia coli strain J5-3. The highest frequency of elimination for both drugs occurred at concentrations and times that produced the lowest survivor levels. 5% of cells were antibiotic-sensitive after 5 h incubation in 5 mg/ml Ara-C, whilst 6 and 7% of the survivors had lost the R factor after 8 and 24 h incubation, respectively in 20 mg/ml HU. The number of survivors began to increase after 5 h incubation in Ara-C, probably due to the inactivation of the drug in the phosphate-buffered medium. All four antibiotic resistances (ampicillin, streptomycin, sulphonamide and tetracycline) mediated by R46 were lost simultaneously and elimination of the whole plasmid was confirmed by conjugation experiments in which the 'cured' cells was shown to be as efficient recipients of R46 as the control R- strain in crosses with E. coli strain J6-2 (R46). No covalently closed circular plasmid DNA was demonstrable in cured cell lines. R+ and R- strains had similar sensitivities to HU but J5-3 R+ was much more sensitive to Ara-C than the isogenic R- strain. It may be concluded that HU eliminates R46 actively whereas although Ara-C may produce some active elimination it acts mainly by selection of R- cells present in the culture.

Culture Media↗