Incompatibility of Escherichia coli rho mutants with plasmids is mediated by plasmid-specific transcription.
The Escherichia coli rho-15 mutant (deficient in transcription termination) is known to be incompatible with pBR322 and other plasmids (J. S. Fassler, G. F. Arnold, and I. Tessman, Mol. Gen. Genet. 204:424-429, 1986). We show that failure of pBR322 to transform rho-15 is mediated by transcription from the tet promoter and readthrough from the tet gene into the rom region. Using an isopropyl-beta-D-thiogalactopyranoside-inducible promoter to replace the tet promoter, we have demonstrated that plasmid-specific transcription inhibits growth of the rho-15 host, possibly due to the expression of the Rom protein. The involvement of Rom protein in pBR322-rho-15 incompatibility is further indicated by the following two experiments. (i) Functional inactivation of the rom gene in pBR322 enabled plasmids to transform E. coli rho-15. (ii) Specific overexpression of the rom gene abolished plasmid transformation into E. coli rho-15. An rpoB8(Ts) mutant RNA polymerase which compensated for the termination defect in E. coli rho-15 also restored plasmid-host compatibility, suggesting that Rom-mediated plasmid-host incompatibility is linked to a defect in transcription termination.
Li
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TK
Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854, USA.
Panchenko
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YA
Drolet
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Liu
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LF
D001426:Bacterial Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005804:Genes, Lethal; D010957:Plasmids; D012234:Rho Factor / Q000502:physiology*; D013753:Tetracycline Resistance; D014158:Transcription, Genetic; D014170:Transformation, Genetic
D001426:Bacterial Proteins; C042833:ROM protein, Bacteria; D012234:Rho Factor