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  • 1
    Electronic Resource
    Electronic Resource
    Benefit of transcription-coupled nucleotide excision repair for gene expression in u.v.-damaged Escherichia coli (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Science Ltd
    Molecular microbiology 18 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of the lactose operon upon induction by IPTG was studied with Escherichia coli B/r and K-12 strains as a function of exposure to ultraviolet light. Patterns of expression inactivation were compared in cells with wild-type UvrABC nucleotide excision repair, with transcription-coupled excision repair (TCR) specifically defective because of a defect at mfd, or with excision repair (ER) and TCR eliminated by defects at uvrA or uvrC. Sets of inactivation patterns were also determined for cells expressing the lactose operon via the ‘UV5’ promoter, an alternative to the wild-type promoter that eliminates dependence of expression on negative DNA supercoiling. The results demonstrated a major contribution by TCR to successful gene expression. Gene expression was more sensitive to u.v. inactivation when TCR was defective and similarly more sensitive when both ER and TCR were defective. Thus, TCR may be the only means of repairing transcription-blocking damage at active genes. Contrasting results with wild-type and UV5 promoters suggested that relaxed supercoiling might accompany repair and reduce expression even though a template lesion is removed. A test of mismatch repair defects on ultraviolet inactivation of gene expression found only limited interference with TCR as it benefits gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_18040615.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of temperature and continuous and interrupted wetness on the infection of pear leaves by conidia of Venturia nashicola (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 54 (2005), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Experiments were conducted to determine: (i) the effects of temperature and duration of continuous wet periods on the infection of pear seedlings by conidia of Venturia nashicola, the causal agent of pear scab; and (ii) the effects of the length and temperature of dry interrupting periods on the mortality of infecting conidia. Average number of scab lesions per leaf increased with increasing duration of wetness. Logistic models adequately described the change in the average number of scab lesions per leaf at 5, 10, 15, 20 and 25°C over the wetness duration. At 30°C, only a few lesions developed. Simple polynomial models satisfactorily described the relationship of the three logistic model parameters (maximum number of lesions, rate of appearance and the time to 50% of the maximum number of lesions) with temperature. The optimum temperature for infection was found to be approximately 20°C. The relationship between mortality and the length of a dry period interrupting an infection process can be satisfactorily described by an exponential model. The rate of mortality at 10, 16 and 22°C did not differ significantly, but was significantly less than that at 28°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3059.2005.01207.x
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  • 3
    Electronic Resource
    Electronic Resource
    Cholecystokinin- and dexfenfluramine-induced anorexia compared using devazepide and c-fos expression in the rat brain
    Amsterdam : Elsevier
    Regulatory Peptides 50 (1994), S. 223-233 
    Details
    ISSN: 0167-0115
    Keywords: 5-Hydroxytryptamine ; Brain mapping ; Feeding ; Immediate early gene ; Ingestive behavior ; MK-329
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-0115(94)90003-5
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  • 4
    Electronic Resource
    Electronic Resource
    RexAB proteins of bacteriophage λ enhance the effect of photolyase-dimer complexes on lacZ gene expression in Escherichia coli (1992)
    Springer
    Molecular genetics and genomics 231 (1992), S. 480-484 
    Details
    ISSN: 1617-4623
    Keywords: Photolyase-dimer complexes ; Lambda genes rexA and rexB ; Superinfection exclusion ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Expression of the lacZ gene in Escherichia coli is inactivated by exposure to ultraviolet light (UV). Inactivation is exceptionally effective when cells contain amplified levels of DNA photolyase (which forms complexes with pyrimidine dimers in the absence of light for actual photoreversal) and a λ prophage. Without amplified photolyase, the λ prophage or both, inactivation rates are similar and much lower. UV-inactivation of lacZ gene expression in the presence of both amplified photolyase and λ is even more effective if λ cI857 is used in place of the wildtype prophage but is wholly unexceptional if the prophage carries defects in the λ genes rexA or rexB. When Rex AB proteins are provided by expression from a plasmid and the cell also contains amplified photolyase, exceptional inactivation rates again obtain; in fact inactivation is most effective under these conditions. The data are considered to reveal a role for Rex AB proteins, which mediate superinfection exclusion, in the exceptional inactivation of gene expression by photolyase bound to pyrimidine dimers in DNA. Photolyase-dimer complexes may mimic the structure of certain complexes that arise during phage development and thus influence Rex A and/or B proteins, thereby shutting down cell metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292719
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  • 5
    Electronic Resource
    Electronic Resource
    Inactivation of lacZ gene expression by UV light and bound DNA photolyase implies formation of extended complexes in the genomes of specific Escherichia coli strains (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 249-257 
    Details
    ISSN: 1617-4623
    Keywords: UV inactivation of β-galactosidase expression ; Genome torsional strain ; DNA photolyase-pyrimidine dimer complexes ; Bacterial nucleoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Escherichia coli strains WU and CS101, UV inactivation of lacZ gene expression is more effective when the cells contain amplified DNA photolyase, and flash photoreactivation (fPR) after 15 min of metabolism does not reverse inactivation by the photolyasedimer complexes. In other strains, also studied with or without amplified DNA photolyase, there is no differential UV inactivation and fPR reverses inactivation by the complexes regardless of continued metabolism. The irreparable condition in strain WU is not due to dysfunction of photolyase: during post-UV metabolism, fPR still restores viability and dimers are removed from the region of the lac operon. When the wild-type lac promoter is repalced by the UV5 promoter, making expression insensitive to relaxed supercoiling and catabolite repression, inactivation by dimers alone becomes more resistant, i.e. requires higher fluences, but inactivation in WU and CS101 is still exceptionally sensitive to photolyasedimer complexes. This indicates that dimers external to the wild-type lac operon may inhibit expression by altering supercoiling but that complexes must involve some other mechanism for their special effect in WU and CS101. The exceptionally efficient inactivation and irreparable condition are consistent with the idea that, in two specific laboratory strains, photolyase bound to dimers at a considerable distance from the lac operon may initiate an aggregation of DNA with other cellular molecules that extends to, and inactivates expression from, the operon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282473
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  • 6
    Electronic Resource
    Electronic Resource
    Mutation frequency decline in Escherichia coli. II. Kinetics support the involvement of transcription-coupled excision repair (1995)
    Springer
    Molecular genetics and genomics 249 (1995), S. 591-599 
    Details
    ISSN: 1617-4623
    Keywords: Targeted mutagenesis ; Excision repair ; Cyclobutane pyrimidine dimers ; Cytosine deamination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutation frequency decline (MFD) in Escherichia coli was examined to demonstrate repair of targeting photoproducts during the post-UV incubation required in this process. Repair of mutation-targeting cyclobutane pyrimidine dimers (T 〈〉 C) was demonstrated when a correlation was established between the mutation frequency normally associated with these lesions and the rate of mutation production at these lesions by spontaneous deamination of cytosines and photoreversal in ung-defective cells. An incubation producing a decline in mutation frequency, i.e., MFD, also produces lower rates of mutation increase via the deamination mechanism. Since the latter assay involves processes entirely within the post-UV incubation period, the lower rates are attributed to rapid transcription-coupled nucleotide excision repair (TCR) that reduces the number of relevant T 〈〉 C dimers during this period. Rediscovery of the neglected fact that MFD can be stimulated by post-UV incubation in buffer alone is part of the analysis. Results presented here and a variety of others are discussed to support a model of MFD as a particular example of TCR: effective repair of photoproducts in the transcribed DNA strand that target glutamine tRNA suppressor mutations occurs during the appropriate post-UV incubation and is responsible for MFD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418028
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  • 7
    Electronic Resource
    Electronic Resource
    Mutation frequency decline in Escherichia coli. I. Effects of defects in mismatch repair (1995)
    Springer
    Molecular genetics and genomics 249 (1995), S. 585-590 
    Details
    ISSN: 1617-4623
    Keywords: UV mutagenesis ; Excision repair ; Mismatch repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutation frequency decline (MFD) in Escherichia coli was examined for effects associated with genetic defects in mismatch repair. The kinetics of MFD are slower when the B/r strain WU3610 carries the mutation mutS201::Tn5 or mutL::Tn10, both of which affect mismatch repair. Similar slow kinetics are produced by mutH34 but not by mutH471::Tn5; the latter has no apparent effect. Strain WU3610-45 (mfd-1) produces the slower kinetics if transcription is inhibited during the post-UV incubation, although it produces no decline in normal circumstances. The slower kinetics are therefore attributed to bulk excision repair that remains when rapid transcription-coupled repair (TCR) is eliminated by certain defects in mismatch repair. A model is proposed wherein mismatch repair defects are thought to slow the activity of TCR but, unlike an mfd defect, not to impede dissociation of stalled transcription complexes at lesions in the transcribed DNA strand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418027
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