Primosome assembly site in Bacillus subtilis.
A single-strand initiation site was detected on the Enterococcus faecalis plasmid pAM beta 1 by its ability to prevent accumulation of single stranded DNA of a rolling circle plasmid, both in Bacillus subtilis and Staphylococcus aureus. This site, designated ssiA, is located on the lagging strand template, approximately 150 bp downstream from the replication origin. ssiA priming activity requires the DnaE primase, the DnaC replication fork helicase, as well as the products of the dnaB, dnaD and dnaI genes of B.subtilis, but not the RNA polymerase. The primase and the replication fork helicase requirements indicate that ssiA is a primosome assembly site. Interestingly, the pAM beta 1 lagging strand synthesis is inefficient when any of the proteins involved in ssiA activity is mutated, but occurs efficiently in the absence of ssiA. This suggests that normal plasmid replication requires primosome assembly and that the primosome can assemble not only at ssiA but also elsewhere on the plasmid. This work for the first time describes a primosome in a Gram-positive bacterium. Involvement of the B.subtilis proteins DnaB, DnaD and DnaI, which do not have any known analogue in Escherichia coli, raises the possibility that primosome assembly and/or function in B.subtilis differs from that in E.coli.
Bruand
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Laboratoire de Génétique Microbienne, Institut de Biotechnologie, INRA-Domaine de Vilvert, Jouy en Josas, France.
Ehrlich
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SD
Jannière
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D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004265:DNA Helicases / Q000378:metabolism; D019915:DNA Primase; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D008954:Models, Biological; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D012316:RNA Nucleotidyltransferases / Q000378:metabolism; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D012321:DNA-Directed RNA Polymerases; D004265:DNA Helicases