Toxicity of the bacteriophage lambda cII gene product to Escherichia coli arises from inhibition of host cell DNA replication.
The bacteriophage lambda cII gene codes for a transcriptional activator protein which is a crucial regulator at the stage of the "lysis-versus-lysogeny" decision during phage development. The CII protein is highly toxic to the host, Escherichia coli, when overproduced. However, the molecular mechanism of this toxicity is not known. Here we demonstrate that DNA synthesis, but not total RNA synthesis, is strongly inhibited in cII-overexpressing E. coli cells. The toxicity was also observed when the transcriptional stimulator activity of CII was abolished either by a point mutation in the cII gene or by a point mutation, rpoA341, in the gene coding for the RNA polymerase alpha subunit. Moreover, inhibition of cell growth, caused by both wild-type and mutant CII proteins in either rpoA(+) or rpoA341 hosts, could be relieved by overexpression of the E. coli dnaB and dnaC genes. In vitro replication of an oriC-based plasmid DNA was somewhat impaired by the presence of the CII, and several CII-resistant E. coli strains contain mutations near dnaC. We conclude that the DNA replication machinery may be a target for the toxic activity of CII.
Kedzierska
Barbara
B
Department of Molecular Biology, University of Gdańsk, Kladki 24, 80-822 Gdańsk, Poland.
Glinkowska
Monika
M
Iwanicki
Adam
A
Obuchowski
Michał
M
Sojka
Piotr
P
Thomas
Mark S
MS
Wegrzyn
Grzegorz
G
D001426:Bacterial Proteins / Q000378:metabolism; D010582:Bacteriophage lambda / Q000235:genetics* / Q000472:pathogenicity; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D053488:DnaB Helicases; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D008242:Lysogeny; D051738:Origin Recognition Complex; D010957:Plasmids; D017354:Point Mutation; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C071702:DnaC protein, E coli; D029968:Escherichia coli Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; D014157:Transcription Factors; D014764:Viral Proteins; C039000:cII protein, bacteriophage lambda; D012321:DNA-Directed RNA Polymerases; C113275:RNA polymerase alpha subunit; D004265:DNA Helicases; D053488:DnaB Helicases