DNA Replication and Repair
The bacteriophageT4 replisome has been proven to be an invaluable system for studying the molecular mechanism of DNA replication. Several decades of studies revealed that despite the variation in number and nature of individual proteins in the T4 replisome as compared to other model systems from viruses, bacteria, archaea, and eukaryotes, the fundamental components that constitute a functional replication fork in bacteriophage T4 faithfully represent other more complex replication systems. We strive to understand the fundamental function and structure of replisomes responsible for DNA replication in general using the reconstituted T4 replisome as a model system.
Similar studies are now being under taken to investigate human holoenzyme assembly from the corresponding clamp loader, clamp and polymerase enzymes followed by biochemical characterization. These data serve as a basis for mechanistic analysis of translesion bypass, one of the pathways for DNA repair.
Purinosome
In vitro investigations of individual enzymes that catalyze the multi-step transformation of a sugar pyrophosphate to a purine have revealed much about their respective mechanism of action. There is little evidence, however, from extra cellular studies for the attractive hypothesis that these enzymes act within a multi-enzyme complex framework. Collaborative efforts using powerful confocal fluorescence methods form the core of an experimental approach to find the locus of these enzymes within eukaryotic cells and have identified a multi-enzyme complex, the purinosome, consisting of the enzymes comprising the de novo purine biosynthetic pathway. The identity of possible additional proteins, the question of why purinosome formation is advantageous to the cell and its relevance as a chemotherapeutic target are future objectives.