Genetic characterization of a prm− mutant of bacteriophage λ
1973; Elsevier BV; Volume: 56; Issue: 1 Linguagem: Inglês
10.1016/0042-6822(73)90308-5
ISSN1096-0341
Autores Tópico(s)Protein Structure and Dynamics
ResumoIt has been hypothesized (Reichardt and Kaiser, 1971) that transcription of the λ genes cI and rex, which code for repressor and rex protein, respectively, can be initiated at either of two sites depending on whether or not repressor itself is present. On infection of a sensitive cell, transcription of repressor (cI) and rex mRNA is thought to be initiated at a “promoter for establishment of repressor synthesis” (pre); however, in an established lysogen, in the presence of active repressor, synthesis of cI-rex mRNA appears to be initiated at a “promoter for maintenance of repressor synthesis” (prm), whose existence has been inferred from several indirect observations (Bode and Kaiser, 1965; Reichardt and Kaiser, 1971; Echols and Green, 1971; Castelazzi et al., 1972). In this communication, we describe the isolation of a mutant defective in prm, the promoter for synthesis of cI-rex mRNA in the presence of repressor (as in an established lysogen). The mutant, prm116, maps at a single site between the cI gene and 0R (the operator to which repressor binds to block rightward transcription of the λ x operon), is phenotypically cI−rex−, and yet complements the pre− mutant cY42 for lysogenization. Thus, its existence precisely locates prm and provides a direct verification of some elements of the two-promoter hypothesis for cI-rex transcription. Since prm116 does not appear to affect repressor binding at 0R, the two sites, prm and 0R, can be separated functionally by mutation.
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