DNA rearrangements generating artificial promoters

Abstract The promoter-cloning plasmid pBRH4 (a derivative of pBR322 with a partially deleted promoter of the tet gene ) is shown to contain a sequence which is located near the Eco RI site and can operate as an effective Pribnow box, but is not the remainder of the deletion-inactivated tet promoter of pBR322. If there is a sequence homologous to the ‘−35’ promoter region at the border of the DNA fragment inserted at the Eco RI site, then a compound promoter arises and activates the tet gene. Point mutations in the nonfunctional −35 region of pBRH4 also activate the cryptic Pribnow box. Several compound promoters were obtained through deleting small portions of DNA around the Hind III site of pBR322; the deletions moved various sequences that could operate as Pribnow boxes towards the −35 region of the tet promoter.