Regulation of replication of plasmid pBR322 in amino acid-starved Escherichia coli strains |
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Authors: | A. Herman A. W?grzyn G. W?grzyn |
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Affiliation: | (1) Department of Molecular Biology, University of Gdansk, Kladki 24, 80-822 Gdask, Poland;(2) Laboratory of Molecular Biology, Marine Biology Center, Polish Academy of Sciences, Kladki 24, 80-822 Gdask, Poland |
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Abstract: | The stringent response causes inhibition of replication of plasmid pBR322 in amino acid-starved Escherichia coli cells whereas in relaxed mutants the replication of this plasmid proceeds for several hours. On the basis of density shift experiments and pulse-labelling experiments we showed that most of the pBR322 molecules begin replication during the relaxed response and the rate of plasmid DNA synthesis in unstarved and isoleucine-starved relA–] bacteria is similar. We found that the Rom function plays a key role in the stringent control of plasmid pBR322 replication, as insertional inactivation of the rom gene causes amplification of pBR322rom– in both relA– and relA+ strains during amino acid starvation. Moreover, pUC19, which is a pBR322-derived plasmid lacking the rom gene, behaves like pBR322rom–, whereas introduction of the rom gene into the pUC19 replicon drives it into the pBR322 mode of replication in amino acid-starved bacteria. A model for the regulation of pBR322 plasmid DNA replication by Rom protein in amino acid-starved Escherichia coli strains is proposed. |
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Keywords: | Stringent control pBR322 replication Rom protein Amino acid starvation |
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