Related Experiment Videos
Identification of the lactococcal exonuclease/recombinase and its modulation by the putative Chi sequence
M el Karoui1, D Ehrlich, A Gruss
1Institut National de la Recherche Agronomique, Jouy en Josas, France.
Summary
Researchers identified a bacterial DNA repair system, RexAB, in Lactococcus lactis that functions similarly to E. coli's RecBCD. This system
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- RecBCD-Chi interactions in Escherichia coli are a model for bacterial recombination.
- Similar interactions were not previously demonstrated in bacteria evolutionarily distant from E. coli.
Purpose of the Study:
- To develop an in vivo model for examining double-stranded DNA (dsDNA) break repair components in diverse microorganisms.
- To identify and characterize the major exonuclease in Lactococcus lactis and investigate its interaction with Chi sites.
Main Methods:
- Development of an in vivo model for dsDNA break repair studies.
- Creation of insertional mutants in Lactococcus lactis screened for exonuclease deficiency.
- Cloning and functional analysis of lactococcal genes (rexAB) in an E. coli recBCD mutant.
Main Results:
- Identified Lactococcus lactis exonuclease (RexAB) and provided evidence for exonuclease-Chi interactions.
- Lactococcal rexAB genes restored UV resistance and recombination proficiency in an E. coli recBCD mutant.
- Lactococcal Chi site (5'-GCGCGTG-3') specifically blocked DNA degradation by RexAB and stimulated recombination 27-fold.
Conclusions:
- RexAB fulfills the biological roles of RecBCD in Lactococcus lactis.
- RexAB activity is modulated by a specific DNA sequence (lactococcal Chi site).
- Exonuclease/recombinase enzymes modulated by short DNA sequences are likely widespread in bacteria.