The tripartite immunity system of phages P1 and P7

FEMS Microbiol Rev. 1995 Aug;17(1-2):121-6. doi: 10.1111/j.1574-6976.1995.tb00193.x.


Prophages P1 and P7 exist as unit copy DNA plasmids in the bacterial cell. Maintenance of the prophage state requires the continuous expression of two repressors: (i) C1 is a protein which negatively regulates the expression of lytic genes including the C1 inactivator gene coi, and (ii) C4 is an antisense RNA which specifically inhibits the synthesis of an anti-repressor Ant. In addition, C1 repression is strengthened by lxc encoding an auxiliary repressor protein. The repressors C1, C4 and Lxc are components of a tripartite immunity system of the two phages. Here, the mode of action of these regulatory components including their antagonists Coi and Ant is described.

Publication types

  • Review

MeSH terms

  • Bacteriophage P1 / immunology*
  • Bacteriophages / immunology*
  • Base Sequence
  • Molecular Sequence Data
  • RNA, Antisense / physiology*
  • Repressor Proteins / physiology*


  • RNA, Antisense
  • Repressor Proteins