Study of the role of PolIV in Pseudomonas aeruginosa lasR mutagenesis

LUJÁN AM; MOYANO AJ; SMANIA AM

San Miguel de Tucumán

Congreso; XLV Reunión Anual de la SAIB; 2009

High prevalence of lasR-deficient Pseudomonas aeruginosa occurring naturally in Cystic Fibrosis chronic lung infections has been shown. However, mutational mechanisms acting on LasR inactivation remain poorly investigated. We previously linked the Mismatch Repair System-deficiency with the emergence of lasR mutants, showing that lasR variants reproducibly emerge at a high frequency from a hypermutator mutS strain. Here, we explored the involvement of transient hypermutability in lasR mutagenesis by studying the role of the error-prone DNA polymerase PolIV (dinB). A dinB null mutant derived from a mutS strain was constructed and the emergence of lasR variants was analyzed. Notably, dinB disruption in a hypermutator background (mutSdinB) resulted in 3 fold increase (P=0.04) in the lasR emergence frequency respect to the mutS strain. Furthermore, over-expression of PolIV in the mutSdinB strain resulted in 16 fold decrease (P=0.04) in lasR emergence. Analysis of the lasR mutational spectra in lasR variants derived from the mutS strain, displayed that lasR inactivation was entirely due to base substitutions (80% C-T transitions). In contrast, 20% of lasR variants emerged from the mutSdinB strain contained -1 frameshift and 80% base substitutions with only 38% being C-T transitions. These results suggest that Pol IV could play an antimutator role in lasR mutagenesis