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Faculty List
Judith Campbell
jcampbel@caltech.edu
Ph.D., 1974, Harvard University
Mechanisms and Regulation of DNA Replication and Repair
The Campbell Group studies DNA replication in the yeast Saccharomyces cerevisiae. Yeast offers an as yet unparalleled ability to combine genetic, molecular, and biochemical approaches in a eukaryotic organism. In the past, biochemistry has focused on the characterization of individual proteins. In modern biochemistry, the emphasis is on studying protein/protein interactions in multienzyme assemblies. In keeping with this trend, our overall goal is to reproduce the assembly and activation of the replication fork at an origin of replication using purified proteins. Our work in preparation for achieving this goal has ranged from defining the structure and activity of chromosomal replication origins, to the discovery of replicative enzymes, verification of their in vivo roles using yeast genetics, and the detailed characterization of their enzymatic mechanisms.
Of central importance in replication are the DNA polymerases. We have used reverse genetics to define the division of labor between the five DNA polymerases in yeast. The big surprise was that there is not just one, but there are no less than three DNA polymerases essential for replication. Our studies have moved into detailed biochemical characterization of the three essential polymerases. These structure/function studies have as their main goal definition of the interactions between the DNA polymerases themselves and between the polymerases and other replication proteins. A central question is to what extent the polymerases act sequentially and to what extent concurrently during replication.
DNA helicases provide the second most important catalytic activity in DNA replication. Helicases are recruited to the origin of replication by specific initiator proteins that recognize and bind to origins. The helicase in turn recruits the polymerase and coordinates unwinding and DNA synthesis. We have recently discovered a DNA helicase that is a good candidate for the key protein that couples the activities of the DNA polymerases. We are studying the interactions of the helicase with origin binding proteins and DNA polymerases - both genetically and biochemically.
