Originally published as Genetics Published Articles Ahead of Print on August 24, 2007.

Genetics, Vol. 177, 723-735, October 2007, Copyright © 2007
doi:10.1534/genetics.107.075861

The Escherichia coli Histone-like Protein HU Has a Role in Stationary Phase Adaptive Mutation

Ashley B. Williams and Patricia L. Foster¹

Department of Biology, Indiana University, Bloomington, Indiana 47405

¹ Corresponding author: Department of Biology, Indiana University, 1001 East Third St., Bloomington, IN 47405.
E-mail: plfoster{at}indiana.edu

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 (Pol IV). Mutations in either of the HU subunits, HU or HUß, decrease adaptive mutation to Lac⁺ by both Pol IV-dependent and Pol IV-independent pathways. Additionally, HU mutations inhibit growth-dependent mutations without a reduction in the level of Pol IV. These effects of HU mutations on adaptive mutation and on growth-dependent mutations reveal novel functions for HU in mutagenesis.

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