umuDC-dnaQ Interaction and its implications for cell cycle regulation and SOS mutagenesis in Escherichia coli.

The Escherichia coli SOS-regulated umuDC gene products participate in a DNA damage checkpoint control and in translesion DNA synthesis. Specific interactions involving the UmuD and UmuD' proteins, both encoded by the umuD gene, and components of the replicative DNA polymerase, Pol III, appear to be important for regulating these two biological activities of the umuDC gene products. Here we show that overproduction of the epsilon proofreading subunit of Pol III suppresses the cold sensitivity normally associated with overexpression of the umuDC gene products. Our results suggest that this suppression is attributable to specific interactions between UmuD or UmuD' and the C-terminal domain of epsilon.