DNA polymerases and SOS mutagenesis: can one reconcile the biochemical and genetic data?
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.
Bridges
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MRC Cell Mutation Unit, University of Sussex, Falmer, Brighton, BN1 9RR, UK. b.a.bridges@sussex.ac.uk
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D016296:Mutagenesis; D013014:SOS Response, Genetics
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C078202:UmuC protein, E coli; C074904:DNA polymerase III, alpha subunit; D004258:DNA Polymerase III; C120926:DNA polymerase V, E coli; D004259:DNA-Directed DNA Polymerase; C055218:UmuD protein, E coli