Molecular and General Genetics MGG

, Volume 238, Issue 3, pp 333–338 | Cite as

pR plasmid replication provides evidence that single-stranded DNA induces the SOS system in vivo

  • Franca Gigliani
  • Carmela Ciotta
  • Maria F. Del Grosso
  • Piero A. Battaglia
Original Articles


Evidence is presented that the pR bat gene is essential for plasmid replication and for spontaneous induction of the SOS response in Escherichia coli. Mutations preventing single-stranded DNA production, needed for pR plasmid replication, also prevent the induction of the SOS system. The following experimental design was used. Firstly, we identified the minima rep region, defined as the minimal DNA sequence necessary for pR plasmid replication and, secondly, analyzed the nucleotide sequence of this region. This identified structures and functions (ori-plus, on-minus and Rep protein) homologous to those found in phages and plasmids replicating by the rolling-circle mechanism. Finally, mutations were introduced either in the replication protein catalytic site or in the nick site consensus sequence, which caused the pR plasmid to lose its ability to induce the SOS system. We conclude that, in this system, the in vivo SOS-inducing signal appears to be the single-stranded DNA produced during pR replication.

Key words

Gram-negative plasmid Rolling circle replication RecA activation 


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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Franca Gigliani
    • 1
  • Carmela Ciotta
    • 1
  • Maria F. Del Grosso
    • 2
  • Piero A. Battaglia
    • 2
  1. 1.Dipartimento di Biopatologia Umana, Sezione di Biologia CellulareUniversity “La Sapienza”, Policlinico UmbertoRomaItaly
  2. 2.Istituto Superiore di SanitàRomaItaly

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