Regulatory Circuits of Bacteriophage Lambda

Abstract

Publisher Summary This chapter summarizes the regulatory systems of λ to point out that both of its developmental pathways follow finely tuned temporal control mechanisms far more sophisticated than those conceived in the past decades. The chapter also emphasizes the salient features of the complex processes, such as: how a multivalent operator makes transcription initiation from two divergent promoters mutually exclusive; how a transcription system is modified to ignore punctuation signals; how the expression of unlinked operons is coordinated; how a viral chromosome integrates into its host chromosome; and how a biological “decision” may be made. Many of these provide new concepts and directions in studying regulatory biology of other systems, both prokaryotic and eukaryotic. Phage λ is a temperate bacterial virus that thrives on a dual, but mutually exclusive, life style. After infection of its host Escherichia coli , it either multiplies and produces progeny viruses by lysing the host or it integrates its own DNA into the host chromosome with concomitant repression of the viral genes by a virus-specific repressor. In the latter case, the inserted viral chromosome is called a “prophage” and is replicated passively as a part of the host chromosome. The cell is said to become lysogenic, and because of the presence of λ repressor is immune to superinfection by a second λ particle.