A 7-base-pair sequence protects DNA from exonucleolytic degradation in Lactococcus lactis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 92; no. 6; pp. 2244 - 2248
• Main Authors: Biswas, I. (National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD.), Maguin, E, Ehrlich, S.D, Gruss, A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 14.03.1995; National Acad Sciences; National Academy of Sciences
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ADN; Bacteria; Base Composition; Base Sequence; Chromosomes; DEGRADACION; DEGRADATION; Deoxyribonucleic acid; DNA; DNA Replication; DNA, Bacterial; DNA, Bacterial - genetics; DNA, Bacterial - metabolism; enzyme activity; Enzymes; Escherichia coli; Escherichia coli - genetics; Exodeoxyribonuclease V; Exodeoxyribonucleases; Exodeoxyribonucleases - genetics; Exodeoxyribonucleases - metabolism; Genetics; Genomes; LACTOCOCCUS LACTIS; Lactococcus lactis - genetics; metabolism; Molecular Sequence Data; NUCLEASAS; NUCLEASE; nucleases; nucleotide sequences; Nucleotides; PLASMIDE; PLASMIDIOS; Plasmids; Polymerase chain reaction; SECUENCIA NUCLEICA; SEQUENCE NUCLEIQUE; Sequencing; Species Specificity; Substrate Specificity; Transcriptional regulatory elements
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.92.6.2244

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.