Biomaterial Database

The ssb-113 allele suppresses the dnaQ49 mutator and alters DNA supercoiling in Escherichia coli. 1997

A Quiñones, and S Neumann

Institut für Genetik, Martin-Luther-Universität, Halle, Germany.

Mutations in the dnaQ gene, which encodes the proofreading epsilon-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 dnaQ49 mutator, because of the involvement of SSB protein in DNA replication. We found that the ssb-113 mutation suppresses the mutator phenotype of dnaQ49. The suppression effect resulted from an enhanced expression of the dnaQ49 allele as determined by experiments with gene fusions. S1 nuclease analysis revealed that the increased dnaQ expression is based on transcriptional activation of the dnaQP2 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 epsilon-subunit of DNA polymerase III may additionally be modulated by DNA supercoiling, and suggest a possible role for DNA topology in mutagenesis.

UI	MeSH Term	Description	Entries
D004258	DNA Polymerase III	A DNA-dependent DNA polymerase characterized in E. coli and other lower organisms but may be present in higher organisms. Use also for a more complex form of DNA polymerase III designated as DNA polymerase III* or pol III* which is 15 times more active biologically than DNA polymerase I in the synthesis of DNA. This polymerase has both 3'-5' and 5'-3' exonuclease activities, is inhibited by sulfhydryl reagents, and has the same template-primer dependence as pol II.	DNA Polymerase delta,DNA-Dependent DNA Polymerase III,DNA Pol III,DNA Dependent DNA Polymerase III,Polymerase III, DNA,Polymerase delta, DNA
D004261	DNA Replication	The process by which a DNA molecule is duplicated.	Autonomous Replication,Replication, Autonomous,Autonomous Replications,DNA Replications,Replication, DNA,Replications, Autonomous,Replications, DNA
D004268	DNA-Binding Proteins	Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.	DNA Helix Destabilizing Proteins,DNA-Binding Protein,Single-Stranded DNA Binding Proteins,DNA Binding Protein,DNA Single-Stranded Binding Protein,SS DNA BP,Single-Stranded DNA-Binding Protein,Binding Protein, DNA,DNA Binding Proteins,DNA Single Stranded Binding Protein,DNA-Binding Protein, Single-Stranded,Protein, DNA-Binding,Single Stranded DNA Binding Protein,Single Stranded DNA Binding Proteins
D004269	DNA, Bacterial	Deoxyribonucleic acid that makes up the genetic material of bacteria.	Bacterial DNA
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D000483	Alleles	Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.	Allelomorphs,Allele,Allelomorph
D015964	Gene Expression Regulation, Bacterial	Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.	Bacterial Gene Expression Regulation,Regulation of Gene Expression, Bacterial,Regulation, Gene Expression, Bacterial