Document Detail

Non-targeted mutagenesis of unirradiated lambda phage in Escherichia coli host cells irradiated with ultraviolet light.
MedLine Citation:
PMID:  6230459     Owner:  NLM     Status:  MEDLINE    
Non-targeted mutagenesis of lambda phage by ultraviolet light is the increase over background mutagenesis when non-irradiated phage are grown in irradiated Escherichia coli host cells. Such mutagenesis is caused by different processes from targeted mutagenesis, in which mutations in irradiated phage are correlated with photoproducts in the phage DNA. Non-irradiated phage grown in heavily irradiated uvr+ host cells showed non-targeted mutations, which were 3/4 frameshifts, whereas targeted mutations were 2/3 transitions. For non-targeted mutagenesis in heavily irradiated host cells, there were one to two mutant phage per mutant burst. From this and the pathways of lambda DNA synthesis, it can be argued that non-targeted mutagenesis involves a loss of fidelity in semiconservative DNA replication. A series of experiments with various mutant host cells showed a major pathway of non-targeted mutagenesis by ultraviolet light, which acts in addition to "SOS induction" (where cleavage of the LexA repressor by RecA protease leads to din gene induction): (1) the induction of mutants has the same dependence on irradiation for wild-type and for umuC host cells; (2) a strain in which the SOS pathway is constitutively induced requires irradiation to the same level as wild-type cells in order to fully activate non-targeted mutagenesis; (3) non-targeted mutagenesis occurs to some extent in irradiated recA recB cells. In cells with very low levels of PolI, the induction of non-targeted mutagenesis by ultraviolet light is enhanced. We propose that the major pathway for non-targeted mutagenesis in irradiated host cells involves binding of the enzyme DNA polymerase I to damaged genomic DNA, and that the low polymerase activity leads to frameshift mutations during semiconservative DNA replication. The data suggest that this process will play a much smaller role in ultraviolet mutagenesis of the bacterial genome than it does in the mutagenesis of lambda phage.
R D Wood; F Hutchinson
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of molecular biology     Volume:  173     ISSN:  0022-2836     ISO Abbreviation:  J. Mol. Biol.     Publication Date:  1984 Mar 
Date Detail:
Created Date:  1984-04-26     Completed Date:  1984-04-26     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985088R     Medline TA:  J Mol Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  293-305     Citation Subset:  IM    
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MeSH Terms
Bacteriophage lambda / genetics*,  radiation effects
Base Sequence / radiation effects
DNA, Viral / genetics
Escherichia coli / genetics,  radiation effects*
Genes, Viral / radiation effects
Plaque Assay
Ultraviolet Rays*
Grant Support
Reg. No./Substance:
0/DNA, Viral

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