Establishing Lysogenic Transcription in the Temperate Coliphage 186

Abstract

A single-copy chromosomal reporter system was used to measure the intrinsic strengths and interactions between the three promoters involved in the establishment of lysogeny by coliphage 186. The maintenance lysogenic promoter p L for the immunity repressor gene cI is intrinsically ϳ20-fold weaker than the lytic promoter p R . These promoters are arranged face-to-face, and transcription from p L is further weakened some 14-fold by the activity of p R . Efficient establishment of lysogeny requires the p E promoter, which lies upstream of p L and is activated by the phage CII protein to a level comparable to that of p R . Transcription of p E is less sensitive to converging p R transcription and raises cI transcription at least 55-fold. The p E promoter does not occlude p L but inhibits lytic transcription by 50%. This interference is not due to bound CII preventing elongation of the lytic transcript. The p E RNA is antisense to the anti-immune repressor gene apl, but any role of this in the establishment of lysogeny appears to be minimal.Temperate bacteriophages provide model systems for studying developmental switches. One question of interest is how these phages achieve efficient and conditional transitions between the lytic and lysogenic alternative developmental states. Bacteriophage lambda, in response to DNA-damaging agents, leaves the lysogenic state and enters lytic development, a process termed prophage induction (7). The reverse transition, establishment of lysogeny, is conditional in lambda upon the activity of a lytic operon gene, cII (9), that responds to the physiology of the infected cell (24). Bacteriophage P2 is the prototype of the second major group of temperate bacteriophages of Escherichia coli (2, 3), and its genome shares very little DNA homology with lambda (4). P2 forms a noninducible prophage and does not require a cII-like gene in order to establish lysogeny (4). However, these traits are not shared by all P2-like phages. Bacteriophage 186 is highly related to P2 (4) yet is like lambda in being SOS inducible (28) and requiring a cII gene for efficient lysogenization (11).Lytic and lysogenic development are controlled in these phages by a stable switch formed by the lytic and lysogenic promoters and the first genes of the divergent lytic and lysogenic operons (Fig.

Modelling Transcriptional Interference and DNA Looping in Gene Regulation

“…Also, the CI system is only a part of the 186 regulatory network and interfaces with other 186 proteins, Apl, CII and Tum. 22,35,36 We hope that our mathematical model for the activity of CI at pR and pL will provide a core around which to build an extended model of the 186 regulatory network to better understand the design of this complex system.…”

Simulating Bacterial Transcription and Translation in a Stochastic π Calculus

“…Both are reflected by the resulting mRna. Such detailed aspects matter when engineering regulatory networks [29], and to the quantitative dynamics of gene expression [67,43], however remain poorly supported in current stochastic simulation packages that tend to emphasize large-scale simulation [55].…”

A comparison of the DNA binding and bending capacities and the oligomeric states of the immunity repressors of heteroimmune coliphages P2 and W

“…Like phage λ the cI gene of phage 186 has two promoters, one for establishment of lysogeny and another for its maintenance. The promoter for establishment of lysogeny is activated by the phage-encoded CII protein (14,15). …”