A five-nucleotide sequence protects DNA from exonucleolytic degradation by AddAB, the RecBCD analogue of Bacillus subtilis.
Homologous recombination in Bacillus subtilis requires the product of the addA and addB genes, the AddAB enzyme. This enzyme, which is both a helicase and a powerful nuclease, is thought to be the counterpart of the Escherichia coli RecBCD enzyme. From this analogy, it is expected that the nuclease activity of AddAB can be downregulated by a specific DNA sequence, which would correspond to the chi site in E. coli. Using protection of linear double-stranded DNA as a criterion, we identified the five-nucleotide sequence 5'-AGCGG-3', or its complement 5'-CCGCT-3', as being sufficient for AddAB nuclease attenuation. We have shown further that this attenuation occurs only if the sequence is properly oriented with respect to the translocating AddAB enzyme. Finally, inspection of the complete B. subtilis genome revealed that this five-nucleotide sequence is over-represented and is, in a majority of cases, co-oriented with DNA replication. Based on these observations, we propose that 5'-AGCGG-3', or its complement, is the B. subtilis analogue of the E. coli chi sequence.
Laboratoire de Génétique Microbienne, Institut National de Recherche Agronomique, Domaine de Vilvert, Jouy en Josas, France.
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D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism*; D004261:DNA Replication / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000235:genetics* / Q000378:metabolism*; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D009713:Nucleotidyltransferases / Q000235:genetics* / Q000378:metabolism*; D011995:Recombination, Genetic
C107954:AadB protein, Acinetobacter sp. SUN; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D009713:Nucleotidyltransferases; C022678:streptomycin 3''-adenylyltransferase; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; D004265:DNA Helicases