Terminus region of the chromosome in Escherichia coli inhibits replication forks.

Abstract

Induction of prophage P2sig5 at 42.degree. C caused replication of the bacterial chromosome in a dnaA mutant of E. coli. The P2sig5 is integrated in this strain near the metG locus, which is a min 47 on the genetic map. The regions of the chromosome replicated after prophage induction were determined by DNA.cntdot.DNA hybridization with various DNA obtained from Proteus mirabilis/E. coli F'' merogenotes and from .lambda. specialized transducing phage. The replication was initiated at the prophage site and was bidirectional. Most of the replication occurred in a counterclockwise direction on the genetic map, and the replication quickly proceeded to the aroD locus (min 37). The replication forks were retarded between aroD and rac (min 31) loci, although the rac locus was finally replicated. A more severe inhibition of replication occurred between the rac and trp (min 27) loci. Possibly, the replication terminus is near the rac locus and the terminus inhibits replication forks.