title: A 7-base-pair sequence protects DNA from exonucleolytic degradation in Lactococcus lactis.
abstract: Linear DNA molecules are subject to degradation by various exonucleases in vivo unless their ends are protected. It has been demonstrated that a specific 8-bp sequence, 5'-GCTGGTGG-3', named Chi, can protect linear double-stranded DNA from the major Escherichia coli exonuclease RecBCD. Chi protects linear replication products of rolling-circle plasmids from RecBCD degradation in vivo, in agreement with observations in vitro. A unique 7-bp sequence, 5'-GCGCGTG-3', is shown to protect similar replication products from degradation in Lactococcus lactis strains but not in more distantly related Gram-positive bacteria. The properties of this sequence in L. lactis correspond to those of a Chi site. Linear plasmid replication products have been detected in numerous prokaryotes, suggesting the widespread existence of short species-specific sequences that preserve linear DNA from extensive degradation by host cell exonucleases.
authors.affiliation: Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, Jouy en Josas, France.
authors.forename: I
authors.initials: I
authors.lastname: Biswas
authors.forename: E
authors.initials: E
authors.lastname: Maguin
authors.forename: S D
authors.initials: SD
authors.lastname: Ehrlich
authors.forename: A
authors.initials: A
authors.lastname: Gruss
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D013294:Lactococcus lactis / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D004269:DNA, Bacterial; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V