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Until recently, it had been concluded from genetic evidence that DNA polymerase III (Pol III, the main replicative polymerase in E. coli) was also responsible for mutagenic translesion synthesis on damaged templates, albeit under the influence of inducible proteins UmuD′ and UmuC. Now it appears that these proteins themselves have polymerase activity (and are now known as Pol V) and can carry out translesion synthesis in vitro in the absence of Pol III. Here I discuss the apparent contradictions between genetics and biochemistry with regard to the role of Pol III in translesion synthesis. Does Pol V interact with Pol III and constitute an alternative component of the replication factory (replisome)? Where do the other three known polymerases fit in? What devices does the cell have to ensure that the “right” polymerase is used in a given situation? The debate about the role of Pol III in translesion synthesis reveals a deeper divide between models that interpret everything in terms of mass action effects and those that embrace a replisome held together by protein–protein interactions and located as a structural entity within the cell. BioEssays 22:933–937, 2000. © 2000 John Wiley & Sons, Inc. |
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