Isolation and Characterization of Virulent HK022 Phage for cI Repressor Analysis
Pierce, Jeffrey C.
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The study of gene regulation has two divergent goals: Increased knowledge of mechanisms, and a deeper understanding of gene regulatory circuitry and its behavior. This work analyzes gene regulation by dissecting the genetic switch in lambdoid phage HK022. Like the highly studied lambda, HK022 undergoes the lysis-lysogeny decision after infecting E. coli. This decision making process is regulated by two proteins, cI and Cro. Both proteins are able to perpetuate their own synthesis while repressing that of the other. The cI repressor was studied here through the isolation of virulent phage, which are those able to grow on a lysogen. Through a series of selections, these mutants were obtained. Each virulent phage was then analyzed for cooperativity defects in the cI gene utilizing indicator screens, cloning and ultimately sequencing. Through the examination of a large number of mutant cI proteins, one may begin to elucidate components of cooperativity, protein-DNA interactions and gene regulation.