Involvement of DnaE, the second replicative DNA polymerase from Bacillus subtilis, in DNA mutagenesis.
In a large group of organisms including low G + C bacteria and eukaryotic cells, DNA synthesis at the replication fork strictly requires two distinct replicative DNA polymerases. These are designated pol C and DnaE in Bacillus subtilis. We recently proposed that DnaE might be preferentially involved in lagging strand synthesis, whereas pol C would mainly carry out leading strand synthesis. The biochemical analysis of DnaE reported here is consistent with its postulated function, as it is a highly potent enzyme, replicating as fast as 240 nucleotides/s, and stalling for more than 30 s when encountering annealed 5'-DNA end. DnaE is devoid of 3' --> 5'-proofreading exonuclease activity and has a low processivity (1-75 nucleotides), suggesting that it requires additional factors to fulfill its role in replication. Interestingly, we found that (i) DnaE is SOS-inducible; (ii) variation in DnaE or pol C concentration has no effect on spontaneous mutagenesis; (iii) depletion of pol C or DnaE prevents UV-induced mutagenesis; and (iv) purified DnaE has a rather relaxed active site as it can bypass lesions that generally block other replicative polymerases. These results suggest that DnaE and possibly pol C have a function in DNA repair/mutagenesis, in addition to their role in DNA replication.
Génétique Microbienne, Institut National de la Recherche Agronomique, Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France. lechat@jouy.inra.fr
Emmanuelle
E
Le Chatelier
Olivier J
OJ
Bécherel
Emmanuelle
E
d'Alençon
Danielle
D
Canceill
S Dusko
SD
Ehrlich
Robert P P
RP
Fuchs
Laurent
L
Jannière
D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins; D018736:DNA Adducts / Q000378:metabolism; D004258:DNA Polymerase III / Q000502:physiology*; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000502:physiology; D016296:Mutagenesis; D013014:SOS Response, Genetics
D001426:Bacterial Proteins; D018736:DNA Adducts; C074904:DNA polymerase III, alpha subunit; C446929:PolC protein, bacteria; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase