Derepression of prophage P2 by satellite phage P4: Cloning of the P4 epsilon gene and identification of its product

作者：Liu T; Renberg SK; HaggardLjungquist E

来源：Journal of Virology, 1997, 71(6): 4502-4508.

Escherichia coli phage P4 lacks all of the genetic information necessary for capsid, tail, and lysis functions, P4 is therefore dependent on a helper phage, such as P2, for lyric propagation. During P4 superinfection of a P2 lysogen, the P2 prophage is derepressed by the action of the P4-encoded epsilon gene, We have cloned the epsilon gene and identified the 10-kDa E protein, The epsilon gene product is the only P4 protein required to derepress prophage P2, which leads to in situ P2 DNA replication, A two-plasmid derepression assay system has been developed to examine the derepression activity of E, The reporter plasmid contains the two face-to-face promoters, Pe and Pc, involved in the lysis-lysogeny transcriptional switch of phage P2 and the immunity repressor C, The Pe promoter is coupled to a car reporter gene, In the construct, the C repressor is transcribed from the Pc promoter and represses the Pe promoter, which mimics the in situ-repressed P2 prophage, The E protein is supplied in trans from a compatible plasmid in which the E gene is under the control of the T7 promoter, We show here that in the two-plasmid assay system, induction of the E protein derepresses the Pe promoter, The ash9 mutation, which is located upstream of the epsilon gene, enhances the E-mediated derepression of the Pe promoter, The purified E protein shows no specific DNA binding activity, and the implications of this are discussed.

• 出版日期1997-6