A missense mutation in the rpoC gene affects chromosomal replication control in Escherichia coli

Abstract

An RNA polymerase mutant with a single-base-pair change in the rpoC gene affects chromosome initiation control. The mutation, which is recessive, is a G to A transition leading to the substitution of aspartate for glycine at amino acid residue 1033 in the RNA polymerase beta' subunit. The chromosome copy number is increased twofold in the mutant at semipermissive growth temperatures (39 degrees C). In a delta oriC strain, in which chromosome initiation is governed by an F replicon, chromosome copy number is not affected. Plasmid pBR322 copy number is also increased in the mutant at 39 degrees C. The mutation causes a more than fivefold increased expression of the dnaA gene at 39 degrees C. It is conceivable that it is this high DnaA concentration which causes the high chromosome copy number and that the mutant RNA polymerase beta' subunit exerts its effect by altering the expression of the dnaA gene. However, other factors must be affected as well to explain why the RNA polymerase mutant can grow in a balanced fashion with a high chromosome concentration. This is in contrast to wild-type cells, which exhibit higher origin concentrations when DnaA protein is overproduced, but in which the overall DNA concentration is only moderately affected.

Rate maintenance of cell division in Escherichia coli B/r: analysis of a simple nutritional shift-down

“…The reduction in cell cycle parameters in the presence of aMG without a significant change in growth rate differs from results of previous studies, in which elongation of the C + D period and reduction in M1 were exerted by low growth rates (2,24,32), mutations (2,23,28), or amino acid deprivation (6). We cannot as yet explain the reduction in these cell cycle parameters caused by aMG.…”

“…The resultant increase of cell size with growth rate, 1/, at least in Escherichia coli and Salmonella typhimurium, is associated with enlargement in both cell dimensions (length and diameter) (26,29,31) with very little change in shape (length/diameter ratio) (30). Mutants with an altered Mi have been isolated, and some biochemical steps have been deciphered (1,2,23,28), but the mechanisms that govern and integrate these processes (initiation and termination of chromosome replication, cell division and shape determination, and chromosome segregation) in the living cell are still obscure (for example, see reference 4).…”

Actin homolog MreB and RNA polymerase interact and are both required for chromosome segregation in Escherichia coli

“…Cells carrying the rpoC907 mutation grew normally at permissive temperature (30°C). In contrast, at semipermissive temperature (39°C), transcription was reduced by ∼50% (Petersen and Hansen 1991). At 30°C, cells of MC1000 rpoC907 had clearly separated nucleoids, whereas growth at 39°C clearly prevented nucleoid segregation (Fig.…”

Mutations in and Monoclonal Antibody Binding to Evolutionary Hypervariable Region of Escherichia coli RNA Polymerase β′ Subunit Inhibit Transcript Cleavage and Transcript Elongation

“…This region is highly variable in proteobacteria and is absent from homologs from most other bacteria, archaea, and eukaryotes. Despite this apparent redundancy, numerous point mutations that altered the termination and elongation properties of E. coli RNAP were localized in the hypervariable region (25,37,38). In addition, mutations in the largest (␤Ј-like) subunit of yeast RNAP II that occurred very close to the hypervariable region dramatically decreased interaction of the enzyme with transcript cleavage factor TFIIS (33).…”