Construction and characterization of pBR322-derived plasmids with deletions of the RNA I region.
A region upstream from the origin of replication in ColE1-type plasmids has been shown to be necessary for replication. Two RNA transcripts are produced from this area, RNA II, which yields the primer for DNA polymerase initiation at the origin and RNA I, which is complementary to the 5' end of RNA II and acts to inhibit primer formation. We have constructed plasmids which do not possess the nucleotide sequence for RNA I, or the normal 5' terminus and promoter of RNA II. The RNA II analog, in these plasmids, is believed to be synthesized by the readthrough transcription of the upstream trimethoprim-resistant dihydrofolate reductase (DHFR) gene at a level comparable to that produced by the tryptophan promoter. These plasmids have a copy number of about tenfold higher than that of pBR322 during logarithmic growth and are compatible with other ColE1-type plasmids. These plasmids are stably maintained in several strains when selective pressure is present and the plasmids are stably maintained during exponential growth in W3110 strains without selective pressure. In all strains examined, the dimeric form of the plasmid was lost from cells much more rapidly than those containing the monomeric form.
R B
RB
Gayle
P S
PS
Vermersch
G N
GN
Bennett
D001483:Base Sequence; D002872:Chromosome Deletion; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004355:Drug Stability; D004926:Escherichia coli / Q000235:genetics*; D005838:Genotype; D007700:Kinetics; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics*; D013045:Species Specificity
C042027:RNA I; D012329:RNA, Bacterial; D012321:DNA-Directed RNA Polymerases