Open AccessEscherichia coli DNA polymerase II catalyzes chromosomal and episomal DNA synthesis in vivo
Author(s) -
Savithri Rangarajan,
Guðmundur A. Guðmundsson,
Zhihao Qiu,
Patricia L. Foster,
Myron F. Goodman
Publication year - 1997
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.94.3.946
Subject(s) - dna polymerase , biology , processivity , microbiology and biotechnology , dna polymerase ii , frameshift mutation , dna polymerase i , polymerase , rna polymerase iii , genetics , mutagenesis , dna , mutation , gene , polymerase chain reaction , rna dependent rna polymerase , reverse transcriptase
We have investigated a role forEscherichia coli DNA polymerase II (Pol II) in copying chromosomal and episomal DNA in dividing cellsin vivo . Forward mutation frequencies and rates were measured at two chromosomal loci,rpoB andgyrA , and base substitution and frameshift mutation frequencies were measured on an F′(lacZ ) episome. To amplify any differences in polymerase error rates, methyl-directed mismatch repair was inactivated. When wild-type Pol II (polB + ) was replaced on the chromosome by a proofreading-defective Pol II exo− (polBex1 ), there was a significant increase in mutation frequencies to rifampicin resistance (RifR ) (rpoB ) and nalidixic acid resistance (NalR ) (gyrA ). This increased mutagenesis occurred in the presence of an antimutator allele ofE. coli DNA polymerase III (Pol III) (dnaE915 ), but not in the presence of wild-type Pol III (dnaE + ), suggesting that Pol II can compete effectively with DnaE915 but not with DnaE+ . Sequencing the RifR mutants revealed a G → A hot spot highly specific to Pol II exo− . Pol II exo− caused a significant increase in the frequency of base substitution and frameshift mutations on F′ episomes, even indnaE + cells, suggesting that Pol II is able to compete with Pol III for DNA synthesis on F episomes.