Premium
The E protein of satellite phage P4 acts as an anti‐repressor by binding to the C protein of helper phage P2
Author(s) -
Liu Tao,
Renberg Sara K.,
HaggårdLjungquist Elisabeth
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.01132.x
Subject(s) - derepression , repressor , biology , lytic cycle , prophage , lysogenic cycle , epitope , bacteriophage , gene , microbiology and biotechnology , lambda phage , temperateness , plasmid , gatad2b , two hybrid screening , function (biology) , biochemistry , genetics , gene expression , antibody , psychological repression , escherichia coli , virus
Temperate phage P2 has the capacity to function as a helper for the defective, unrelated, satellite phage P4. In the absence of a helper, P4 can either lysogenize its host or establish itself as a plasmid. For lytic growth, P4 requires the structural genes, packaging and lysis functions of the helper. P4 can get access to the late genes of prophage P2 by derepression, which is mediated by the P4 E protein. E has been hypothesized to function as an anti‐repressor. To locate possible epitopes interacting with E, an epitope display library was screened against E, and the most frequent sequence found had some identities to a region within P2 C. Using the yeast two‐hybrid system, a clear activation of a reporter gene was found, strongly supporting an interaction between E and C. The P2 C repressor is believed to act as a dimer, which is confirmed in this work using in vivo dimerization studies. The E protein was also found to form dimers in vivo . The E protein only affects dimerization of C marginally, but the presence of E enhances multimeric forms of C. Furthermore, binding of the C protein to its operator is inhibited by E in vitro , indicating that the anti‐repressor function of E is mediated by the formation of multimeric complexes of E and C that interfere with the binding of C to its operator.