Replication of a Bacillus Subtilis oriC Plasmid in Vitro

摘要

Recently several oriC plasmids have been isolated from various bacterialchromosomes in addition to that from Escherichia coil. These include Pseudomonas putida (Yee and Smith, 1990), Streptomyces lividans (Zakrzewska-Czerwinska and Schrempf, 1992) and Bacillus subtilis (Moriya et al., 1992). In each case the oriC is characterized by the presence of Dna A box regions: untranslatable regions containing multiple repeats of the Dna A box (the binding sequence of the DNA protein) (Fig. 1). In E. coil, the interaction of the Dna A protein with the Dna A boxes in oriC is a primary event in the initiation of chromosomal replication (Bramhill and Kornberg, 1988a). This is also the case with B. subtilis. Thus, we have found that a Dna A mutant was defective in the initiation of chromosomal replication at the restrictive temperature (Moriya et al., 1990); that the purified Dna A protein bound to DNA boxes in oriC (Fukuoka et al., 1990); and that mutation in Dna A boxes within a Dna A box region affected the initiation frequency of chromosomal replication (Moriya et al, 1988). These results strongly suggest that the interaction between the Dna A protein and Dna A boxes in Dna A box regions commonly play an essential role in initiation and regulation of chromosomal replication in bacteria.