Chapter 13 Regulation of Lytic Development

Abstract

The lytic response to infection by phage λ involves an ordered, temporal expression of viral genes, culminating in cell lysis and release of new virus particles. In this process of lytic development, the genes concerned with DNA replication, genetic recombination, and regulation are expressed early after infection; the genes for phage head and tail formation and cell lysis are expressed late. This chapter will deal mainly with how regulation of lytic development occurs. The alternative lysogenic response to infection requires an interruption of lytic development through the action of regulatory genes which provide for repression of lytic functions. This process is discussed in Chapters 11 and 12.

The study of regulation by phage λ shares the same goals as parallel studies with bacterial or other viral systems. These goals can be summarized as three general questions. First, is regulation positive or negative? — do the regulatory elements act to turn on or to turn off the genes under their control? Second, what is the cellular level of regulation?—do the regulatory elements act by influencing RNA synthesis, RNA degradation, protein synthesis? Third, what is the molecular mechanism by which the regulatory elements exert their control?—is the regulatory element a protein?—does it bind to DNA?—etc.

These questions were first brought into sharp focus by Jacob and Monod (1961). Jacob and Monod provided strong genetic evidence for the existence of a regulatory element (“a repressor”) for the cluster of genes concerned with lactose metabolism (the lac operon). They also pointed...