Expression of the rtp gene of Bacillus subtilis is required for replication fork arrest at the chromosome terminus

It was earlier proposed that clockwise replication fork arrest at the chromosome terminus in Bacillus subtilis is dependent upon expression of the rtp gene adjacent to the site of arrest, terC [Smith and Wake, J. Bacteriol. 170 (1988) 4083-4090]. A merodiploid strain of B. subtilis, in which rtp was placed under the control of the IPTG-inducible spac-1 promoter, was constructed. Replication fork arrest at terC, as monitored by the level of a forked DNA molecule of predicted dimensions, was shown to be dependent upon IPTG-induced expression of rtp in this strain. The very low concentration of IPTG needed to induce a substantial level of fork arrest suggests that relatively little RTP, the protein product of rtp, is needed for fork arrest at terC.