Permeabilized Cells

Permeabilized cells allow measurement of authentic replicative DNA synthesis. They are notable for ease of preparation and a minimal disturbance of the replicative apparatus. The limitation is that there is no initiation of new cycles of DNA replication. Such systems serve well to monitor the effects of agents on DNA replication or repair since they allow ready definition of the category of synthesis. Permeable cell systems are useful for defining the biochemical requirements and responses of DNA replication and repair. Permeable cells are used to examine the role of DNA polymerases in response to hydrogen peroxide damage, showing that cells have more than one repair pathway in that response. In human fibroblasts, the use of inhibitors specific for different polymerases allows identification of the roles of these enzymes in response to damage secondary to mutagens. Use of mutants with defined deficiencies is much less available in permeable human cells than in bacterial cells. Permeable cell systems offer the advantage of testing the cellular response to low-molecular-weight agents in a situation representing minimal pertubation of the replisome.