The Role of DNA Polymerase I in Excision-Repair
The ability of three different DNA polymerase I mutants of Escherichia coli to carry out excision-repair was examined. Strains having the same genetic origin but carrying either the polA1,po1A107, rsA1, or pot + alleles were compared. The rate of ultraviolet-induced dimer excision was slightly reduced, relative to that found in Pol+ strains, in the PolAl strain; greatly reduced in the Po1A107 strain; and found not to occur in the ResAl strain. Ultraviolet-light-induced repair synthesis as determined by the ultraviolet-stimulated incorporation of 3H-labeled 5-bromo-2′ -deoxyuridine into DNA of the parental density showed that the polAl mutation resulted in an increase in repair replication, while the presence of the polA107 allele caused a reduction in the amount of repair synthesis relative to that of the Pol+ strain. The ResAl strain, however, showed no ultraviolet stimulation of the incorporation of the density label. These observations indicate that DNA polymerase I plays a key role in the excision-repair process in E. coli.
KeywordsPolymerize Activity Parental Density Pyrimidine Dimer polAl Mutation Repair Synthesis
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