Functional analysis of the interaction between the mismatch repair protein MutS and the replication processivity factor β clamp in Pseudomonas aeruginosa

Abstract

Interaction between MutS and the replication factor B clamp has been extensively studied in a Mismatch Repair context; however, its functional consequences are not well understood. We have analyzed the role of the MutS-B clamp interaction in Pseudomonas aeruginosa by characterizing a clamp binding motif mutant, denominated MutSB, which does not interact with the replication factor. A detailed characterization of P. aeruginosa strain PAO1 harboring a chromosomal mutSB allele demonstrated that this mutant strain exhibited mutation rates to rifampicin and ciprofloxacin resistance comparable to that of the parental strain. mutSB PAO1 was a proficient as the parental strain for DNA repair under highly mutagenic conditions imposed by the adenine base analog 2-aminopurine. In addition, using a tetracycline resistance reversion assay to assess the repair of a frameshift mutation, we determined that the parental and mutSbeta strains exhibited similar reversion rates. Our results clearly indicate that the MutS-B clamp interaction does not have a central role in the methylation-independent Mismatch Repair of P. aeruginosa.