PhD, University of Wisconsin, 1970
Replication of cellular chromosomes is a vital process that is precisely coordinated with cell division. To learn more about the molecular events that underlie chromosomal DNA replication, we have developed an in vitro system, composed of 20 highly purified proteins, that specifically replicates supercoiled chromosomes that carry a bacteriophage lambda replication origin. Our studies of this prototype model system indicate that nucleoprotein structures with novel properties are assembled at the origin prior to replication initiation. We have discovered that partial disassembly of these multiprotein structures is required both for the unwinding of DNA and for initiation of DNA chain elongation and have demonstrated that this protein-remodeling event is mediated by a universally conserved molecular chaperone team.
Our current efforts are focused towards elucidating precisely how synergistic protein-protein interactions in complex nucleoprotein structures contribute to "activation" and opening of origin DNA and to the specific loading of a DNA helicase ring on each DNA strand at the origin. In other studies, we are examining how molecular chaperones (i) cooperate to select protein targets and (ii) harness the energy of ATP binding and hydrolysis to energize protein remodeling events. We combine biochemical, molecular biological, biophysical, kinetic, and genetic approaches in our analyses of the structure and function of key macromolecular assemblies.