Proofreading-defective DNA polymerase II increases adaptive mutation in Escherichia coli.

Abstract:

The role of Escherichia coli DNA polymerase (Pol) II in producing or avoiding mutations was investigated by replacing the chromosomal Pol II gene (polB+) by a gene encoding an exonuclease-deficient mutant Pol II (polBex1). The polBex1 allele increased adaptive mutations on an episome in nondividing cells under lactose selection. The presence of a Pol III antimutator allele (dnaE915) reduced adaptive mutations in both polB+ cells and cells deleted for polB (polB delta 1) to below the wild-type level, suggesting that both Pol II and Pol III are synthesizing episomal DNA in nondividing cells but that in wild-type cells Pol III generates the adaptive mutations. The adaptive mutations were mainly -1 frame-shifts occurring in short homopolymeric runs and were similar in wild-type, polB delta 1, and polBex1 strains. Mutations produced by both Pol III and Pol II ex1 were corrected by the mutHLS mismatch repair system.

Polymerases:

Topics:

Exonuclease Activity

Status:

new topics/pols set partial results complete validated

Results:

Polymerase Reference Property Result Context
Eco Pol II Foster PL1995 3-5' Exonuclease (proofreading) Yes
Eco Pol II exo- Foster PL1995 3-5' Exonuclease (proofreading) No

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