The replicative polymerases PolC and DnaE are required for theta replication of the Bacillus subtilis plasmid pBS72.
Plasmids are the tools of choice for studying bacterial functions involved in DNA maintenance. Here a genetic study on the replication of a novel, low-copy-number, Bacillus subtilis plasmid, pBS72, is reported. The results show that two plasmid elements, the initiator protein RepA and an iteron-containing origin, and at least nine host-encoded replication proteins, the primosomal proteins DnaB, DnaC, DnaD, DnaG and DnaI, the DNA polymerases DnaE and PolC, and the polymerase cofactors DnaN and DnaX, are required for pBS72 replication. On the contrary, the cellular initiators DnaA and PriA, the helicase PcrA and DNA polymerase I are dispensable. From this, it is inferred that pBS72 replication is of the theta type and is initiated by an original mechanism. Indirect evidence suggests that during this process the DnaC helicase might be delivered to the plasmid origin by the weakly active DnaD pathway stimulated by a predicted interaction between DnaC and a domain of RepA homologous to the major DnaC-binding domain of the cellular initiator DnaA. The plasmid pBS72 replication fork appears to require the same functions as the bacterial chromosome and the unrelated plasmid pAMbeta1. Most importantly, this replication machinery contains the two type C polymerases, PolC and DnaE. As the mechanism of initiation of the three genomes is substantially different, this suggests that both type C polymerases might be required in any Cairns replication in B. subtilis and presumably in other bacteria encoding PolC and DnaE.
Titok
Marina
M
Belarussian State University, Biological Faculty, Department of Genetics and Biotechnology, Minsk 220050, 4 Scorina Avenue, Belarus.
Suski
Catherine
C
Memorial Sloan-Kettering Cancer Center, NY 10021, USA.
Dalmais
Bérengère
B
Laboratoire de Génétique Microbienne, Bâtiment des Biotechnologies, INRA, 78352 Jouy en Josas, France.
Ehrlich
S Dusko
SD
Laboratoire de Génétique Microbienne, Bâtiment des Biotechnologies, INRA, 78352 Jouy en Josas, France.
Jannière
Laurent
L
Laboratoire de Génétique Microbienne, Bâtiment des Biotechnologies, INRA, 78352 Jouy en Josas, France.
D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D004265:DNA Helicases / Q000235:genetics / Q000502:physiology; D004258:DNA Polymerase III / Q000235:genetics / Q000502:physiology*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000502:physiology*; D023061:Gene Order; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D018741:Replication Origin / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D015534:Trans-Activators; C045264:replication initiator protein; C074904:DNA polymerase III, alpha subunit; C446929:PolC protein, bacteria; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D004265:DNA Helicases