Involvement of the ribulosephosphate epimerase gene in the dnaA and dnaR functions for initiation of chromosome replication in Escherichia coli

Abstract

Initiation of replication of the Escherichia coli chromosome is rendered temperature-sensitive by the dnaR130 mutation in the prs gene that encodes phosphoribosylpyrophosphate synthetase. The thermosensitivity of the dnaR mutant is suppressed by a spontaneous mutation in rpe, the gene encoding ribulosephosphate epimerase. Disruption of the rpe gene reverses the thermosensitive growth of the dnaR mutant. The rpe-disrupted dnaR mutant exhibits extensive DNA synthesis at low and high temperatures, as does the dnaR+ rpe disruptant and the dnaR+ rpe+ strain. The thermoresistant DNA synthesis in the rpe dnaR double mutant is dnaA dependent, because the dnaA167 mutation renders the synthesis thermosensitive. The rpe-knockout mutation abolishes the ability of the dnaA115 allele to complement the defect of the dnaA167 mutant with or without the dnaR mutation and diminishes the dnaR-complementing ability of the dnaR224 allele. These results show that the rpe product is involved in the functions of the products of both dnaA and dnaR for initiation of replication of the bacterial chromosome.