Establishing Lysogenic Transcription in the Temperate Coliphage 186

AUTOR(ES)
FONTE

American Society for Microbiology

RESUMO

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 pL for the immunity repressor gene cI is intrinsically ∼20-fold weaker than the lytic promoter pR. These promoters are arranged face-to-face, and transcription from pL is further weakened some 14-fold by the activity of pR. Efficient establishment of lysogeny requires the pE promoter, which lies upstream of pL and is activated by the phage CII protein to a level comparable to that of pR. Transcription of pE is less sensitive to converging pR transcription and raises cI transcription at least 55-fold. The pE promoter does not occlude pL but inhibits lytic transcription by 50%. This interference is not due to bound CII preventing elongation of the lytic transcript. The pE RNA is antisense to the anti-immune repressor gene apl, but any role of this in the establishment of lysogeny appears to be minimal.

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