ROLE OF THE REPLICATION PROCESSIVITY FACTOR ß CLAMP IN THE MISMATCH REPAIR OF Pseudomonas aeruginosa

MONTI MARIELA R.; MIGUEL VIRGINIA; BORGOGNO MARÍA V.; CARLOS E. ARGARAÑA

Congreso; XLVII Reunión Anual de SAIB; 2011

The DNA mismatch repair system (MRS) removes nucleotides misincorporated during DNA replication and regulates the recombination between divergent sequences. It has been proposed that the replication processivity factor ß clamp can play a role in the initiation of MRS, by targeting the repair protein MutS to areas of active DNA replication, and in the discrimination of the newly synthesized strand. We have analyzed the role of MutS-ß clamp interaction in Pseudomonas aeruginosa by characterizing two MutS mutant versions that do not interact with the replication factor: a C-terminal deletion mutant (MutS798) and a ß clamp binding motif mutant (MutSß). A detailed analysis of MutS798 and MutSß function demonstrated that both mutants were proficient in mismatch repair even under mutagenic conditions, as we determined by measuring mutation rates to rifampicin and ciprofloxacin resistance and reversion of a +1G mutation. These results clearly indicate that MutS-ß clamp interaction is not required for a proper MRS activity in P. aeruginosa. However, determination of the molecular basis of resistance to rifampicin and ciprofloxacin revealed that MutSß produced a mutation spectrum different from wild type MutS and unrelated to mutS deficiency. At present, we are analyzing the biochemical properties of MutSß, and if the affinity of MutS for different heteroduplexes is regulated by ß clamp.