We show that temperature-sensitive mutations in dnaZ, the gene for the gamma subunit of DNA polymerase III holoenzyme, can be suppressed by mutations in the dnaN gene, which encodes the beta subunit. These results support a direct physical interaction of these two subunits during polymerase assembly or function. The suppressor phenotype is also sensitive to modulation by the dnaA genotype. Since dnaA is organized in an operon with dnaN, and dnaA is a regulatory gene of this operon, we propose that the dnaA effect on suppression can best be explained by modulation of suppressor dnaN levels.