New complexities of SOS-induced "untargeted" mutagenesis in Escherichia coli as revealed by mutation accumulation and whole-genome sequencing.
DNA Repair (Amst)
; 90: 102852, 2020 06.
Article
em En
| MEDLINE
| ID: mdl-32388005
ABSTRACT
When its DNA is damaged, Escherichia coli induces the SOS response, which consists of about 40 genes that encode activities to repair or tolerate the damage. Certain alleles of the major SOS-control genes, recA and lexA, cause constitutive expression of the response, resulting in an increase in spontaneous mutations. These mutations, historically called "untargeted", have been the subject of many previous studies. Here we re-examine SOS-induced mutagenesis using mutation accumulation followed by whole-genome sequencing (MA/WGS), which allows a detailed picture of the types of mutations induced as well as their sequence-specificity. Our results confirm previous findings that SOS expression specifically induces transversion base-pair substitutions, with rates averaging about 60-fold above wild-type levels. Surprisingly, the rates of GC to CG transversions, normally an extremely rare mutation, were induced an average of 160-fold above wild-type levels. The SOS-induced transversion showed strong sequence specificity, the most extreme of which was the GC to CG transversions, 60% of which occurred at the middle base of 5'GGC3'+5'GCC3' sites, although these sites represent only 8% of the GC base pairs in the genome. SOS-induced transversions were also DNA strand-biased, occurring, on average, 2- to 4- times more often when the purine was on the leading-strand template and the pyrimidine on the lagging-strand template than in the opposite orientation. However, the strand bias was also sequence specific, and even of reverse orientation at some sites. By eliminating constraints on the mutations that can be recovered, the MA/WGS protocol revealed new complexities of SOS "untargeted" mutations.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Resposta SOS em Genética
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Mutagênese
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Escherichia coli
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Mutação
Idioma:
En
Revista:
DNA Repair (Amst)
Assunto da revista:
BIOLOGIA MOLECULAR
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BIOQUIMICA
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Estados Unidos