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Expression of the dnaB gene of Escherichia coli is inducible by replication- blocking DNA damage in a recA-independent manner. Paper-416389. The DnaB protein is a component of the phi X-type primosome which is regarded as a model system for lagging strand synthesis of the chromosome.
The replicative DNA helicase encoded by the dnaB gene is essential for chromosomal DNA replication in Escherichia coli. Paper-416389.
Comparative S1 analysis of transcripts in untreated and induced cells demonstrated that the induction is due to increased transcription from the dnaB promoter. Paper-416389.
Using translational lacZ fusions at the plasmid and chromosomal levels, we studied the influence of DNA-damaging agents on dnaB gene expression. Paper-416389.
We found that DNA damage caused by mitomycin C, methyl methanesulphonate, 4-nitro-quinoline N-oxide, and UV irradiation led to a moderate, but significant induction of dnaB gene expression. Paper-416389.
Moreover, the data suggest that replication proteins are involved in recovery from replication-blocking DNA damage in two different ways--on the one hand at the level of initiation and on the other hand at the level of elongation.
These results show that the induction of dnaB gene expression by replication-blocking DNA damage is due to a mechanism other than the indirectly SOS-dependent induction of the other DNA replication genes. Paper-416389.
In contrast to other DNA damage-inducible replication genes, such as dnaA, dnaN, dnaQ, and polA, expression of which is not inducible in recA and lexA mutants, the induction of dnaB was also observed in a recA1 mutant. Paper-416389.
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