In vitro mutagenesis and SOS repair.
SOS repair in Escherichia coli (E. coli) utilizes inducible gene products to "fix" mutations in the genome. It has been supposed that an "error prone" system is induced which makes errors in the course of bypassing lesions. An alternative model has been proposed by Bridges and Woodgate which suggests that it is the elongation step rather than the insertion opposite a damaged site which is critical in SOS mutagenesis. A variety of in vitro evidence supports this more recent model. DNA polymerases can be shown to insert bases opposite non-instructional lesions in DNA. It can be demonstrated that it is the elongation rather than the insertion step which is rate limiting in such in vitro reactions. An in vitro mutagenesis system can be devised using a processive polymerase with a reduced 3'----5' exonuclease activity. This system mimics the mutagenic specificity seen in vivo.
Strauss
B S
BS
D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics*; D009154:Mutation; D013014:SOS Response, Genetics