ROLE OF MISMATCH REPAIR SYSTEM IN THE GENETIC RECOMBINATION OF Pseudomonas aeruginosa

BORGOGNO MARÍA V; MONTI MARIELA R; ARGARAÑA CARLOS E

Congreso; XLVIII Reunión Anual de SAIB; 2012

The DNA Mismatch Repair (MMR) is a physiologic mechanism to prevent post-replicative mutations and/or recombination between partially homologous sequences. To analyze the recombination process in P. aeruginosa, we previously constructed a LacZ-based system to measure recombination in vivo between identical (homologous) or partially divergent (homeologous) DNA sequences. Here, we show that the DNA divergence reduced the recombination rate by 38-fold in a wild type strain. Inactivation of either mutS or mutL gene significantly increased the homeologous recombination respect to a wild type strain (~28-fold for mutS and ~370-fold for mutL). These mutants also affected the recombination rate between identical sequences, although in a lesser extent (~4-fold for mutS and ~15-fold for mutL). In addition, we determined that mutant strains expressing MutSR842E (a full-length dimeric version of MutS) or MutS (a MutS version unable to interact with ßclamp)were as proficient as the wild type strain to inhibit the homeologous recombination. These results indicate that both homologous and homeologous recombination are affected by the absence of MMR factors whereas the oligomerization state of MutS as well as its interaction with ß-clamp do not have any effect.We are currently analyzing the proficiency of MutS and MutL to inhibit the recombination catalyzed by RecA in a vitro system.