The Escherichia coli histone-like protein HU has a role in stationary phase adaptive mutation

Stationary phase adaptive mutation in Escherichia coli is thought to be a mechanism by which mutation rates are increased during stressful conditions, increasing the possibility that fitness-enhancing mutations arise. Here we present data showing that the histone-like protein, HU, has a role in the molecular pathway by which adaptive Lac⁺ mutants arise in E. coli strain FC40. Adaptive Lac⁺ mutations are largely but not entirely due to error-prone DNA polymerase IV. Mutations in either of the HU subunits, HUor HU, decrease adaptive mutation to Lac⁺ by both Pol IV-dependent and Pol IV independent pathways. In contrast, HU mutations inhibit growth-dependent mutations by reducing the levels of Pol IV. These differences in the effects of HU mutations on adaptive mutation and on growth dependent mutations reveal fundamental new differences in these pathways.

Key Words: DNA Polymerase IV, HU protein, adaptive mutation, mutagenesis, recombination

Online ISS 1091-6490
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