biostudies-literatureUnknown95(2)el Karoui MStudies of RecBCD-Chi interactions in Escherichia coli have served as a model to understand recombination events in bacteria. However, the existence of similar interactions has not been demonstrated in bacteria unrelated to E. coli. We developed an in vivo model to examine components of dsDNA break repair in various microorganisms. Here, we identify the major exonuclease in Lactococcus lactis, a Gram-positive organism evolutionarily distant from E. coli, and provide evidence for exonuclease-Chi interactions. Insertional mutants of L. lactis, screened as exonuclease-deficient, affected a single locus and resulted in UV sensitivity and recombination deficiency. The cloned lactococcal genes (called rexAB) restored UV resistance, recombination proficiency, and the capacity to degrade linear DNProceedings of the National Academy of Sciences of the United States of America626-31https://www.ebi.ac.uk/biostudies/studies/S-EPMC18471biostudies-literatureIdentification of the lactococcal exonuclease/recombinase and its modulation by the putative Chi sequence.PMC18471Ehrlich DGruss Ael Karoui MfalseIdentification of the lactococcal exonuclease/recombinase and its modulation by the putative Chi sequence.Studies of RecBCD-Chi interactions in Escherichia coli have served as a model to understand recombination events in bacteria. However, the existence of similar interactions has not been demonstrated in bacteria unrelated to E. coli. We developed an in vivo model to examine components of dsDNA break repair in various microorganisms. Here, we identify the major exonuclease in Lactococcus lactis, a Gram-positive organism evolutionarily distant from E. coli, and provide evidence for exonuclease-Chi interactions. Insertional mutants of L. lactis, screened as exonuclease-deficient, affected a single locus and resulted in UV sensitivity and recombination deficiency. The cloned lactococcal genes (called rexAB) restored UV resistance, recombination proficiency, and the capacity to degrade linear DN1998-01-01T00:00:00Z1998 Jan2025-04-04T22:05:53.994Z2019-03-26T23:45:21ZS-EPMC18471943524310.1073/pnas.95.2.626