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The ssb ‐113 allele suppresses the dnaQ 49 mutator and alters DNA supercoiling in Escherichia coli
Author(s) -
Quiñones Ariel,
Neumann Susanne
Publication year - 1997
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1997.4531718.x
Subject(s) - dna supercoil , biology , microbiology and biotechnology , dna polymerase , dna polymerase ii , dna clamp , dna , mutagenesis , genetics , mutant , dna replication , dna polymerase delta , gene , polymerase chain reaction , reverse transcriptase
Mutations in the dnaQ gene, which encodes the proofreading ε‐subunit of the DNA polymerase III holoenzyme, lead to a mutator phenotype caused by enhanced error rates during DNA replication. In this paper, we studied the influence of ssb mutations on the dnaQ 49 mutator, because of the involvement of SSB protein in DNA replication. We found that the ssb ‐113 mutation suppresses the mutator phenotype of dnaQ 49. The suppression effect resulted from an enhanced expression of the dnaQ 49 allele as determined by experiments with gene fusions. S1 nuclease analysis revealed that the increased dnaQ expression is based on transcriptional activation of the dnaQ P2 promoter. This seems to be the consequence of an increased DNA supercoiling in the ssb ‐113 mutant, which also influenced further functions that are sensitive to alterations in DNA supercoiling. These results support the hypothesis that the expression of the ε‐subunit of DNA polymerase III may additionally be modulated by DNA supercoiling, and suggest a possible role for DNA topology in mutagenesis.