title: Origin-specific reduction of ColE1 plasmid copy number due to mutations in a distinct region of the Escherichia coli RNA polymerase.
abstract: Mutations affecting a region of the Escherichia coli RNA polymerase have been isolated that specifically reduce the copy number of ColE1-type plasmids. The mutations, which result in a single amino acid alteration (G1161R) or a 41-amino acid deletion (Delta1149-1190) are located near the 3'-terminal region in the rpoC gene, which encodes the largest subunit (beta ') of the RNA polymerase. The rpoC deletion and the point mutation cause over 20- and 10-fold reductions, respectively, in the copy number of ColE1. ColE1 plasmid numbers are regulated by two plasmid-encoded RNAs: RNA II, which acts as a preprimer for the DNA polymerase I to start initiation of replication, and RNA I, its antisense inhibitor. Altered expression from the RNA I and RNA II promoters in vivo was observed in the RNA polymerase mutants. The RNA I/RNA II ratio is higher in the mutants than in the wild-type strain and this is most probably the main reason for the reduction in the ColE1 copy number in the two rpoC mutants.
authors.affiliation: Department of Microbiology, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Ederth
authors.forename: Leif A
authors.initials: LA
authors.lastname: Isaksson
authors.forename: F
authors.initials: F
authors.lastname: Abdulkarim
mesh_terms: D019943:Amino Acid Substitution; D015153:Blotting, Western; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004926:Escherichia coli; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012270:Ribosomes / Q000378:metabolism; D017384:Sequence Deletion
chemical_list: D012321:DNA-Directed RNA Polymerases; D009699:N-Glycosyl Hydrolases