NSF Award
8718115
The goal of this project is to understand the interaction of DNA gyrase with intracellular bacterial DNA. The specific objectives are: l. to establish quantitative relationships between the occupation of sites in DNA, with which gyrase intereacts strongly, and the superhelix density of the DNA molecule in which the sites reside. 2. to examine how transcription influences the interaction of gyrase with particular sites in plasmid DNA in the vicinity of a strong, inducible promoter. 3. to map naturally occurring sites on the chromosome where gyrase interacts with DNA in the vicinity of an inducible operon before and after induction, and 4. to study the dynamics of gyrase-chromosome interactions. The latter studies will include chromosomal and cytoplasmic gyrase are in rapid exchange, whether cytoplasmic gyrase shows a preference for binding to newly-replicated DNA or for binding to actively transcribing DNA, and whether gyrase exhibits a preference for binding to DNA during specific phases of the cell cycle. The chromosome of E. coli exists as a circular DNA molecule that must be compacted more than 1000-fold in order to fit inside the cell. Compaction is accomplished in part by supercoiling or twisting of the DNA as a result of the action of the enzymes known as topoisomerses that control DNA supercoiling. In addition to compacting the genome, supercoiling also influences many of the biological activities of DNA such as transcription and replication. Dr. Drlica's project is designed to investigate the interactions that occur between gyrase and the bacterial chromosome and to determine the relationship between supercoiling and gene expression.
