Translesion DNA polymerases are required for spontaneous deletion formation in Salmonella typhimurium
2009 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, no 25, 10248-10253 p.Article in journal (Refereed) Published
How spontaneous deletions form in bacteria is still a partly unresolved problem. Here we show that deletion formation in S. typhimurium requries the presence of functional translesion polymerases. First, in wild type bacteria, removal of the known translesion DNA polymerases: PolII (polB), PolIV (dinB), PolV (umuDC) and the PolV homologue SamAB (samAB) resulted in a 10-fold decrease in the deletion rate, indicating that 90% of all spontaneous deletions require these polymerases for their formation. Second, overexpression of these polymerases by de-repression of the DNA damage-inducible LexA regulon caused a 25-fold increase in deletion rate that depended on the presence of functional translesion polymerases. Third, overexpression of the polymerases PolII and PolIV from a plasmid increased the deletion rate 12- to 30-fold respectively. Last, in a recBC- mutant where dsDNA ends are stabilized due to the lack of the end-processing nuclease RecBC, the deletion rate was increased 20-fold. This increase depended on the translesion polymerases. In lexA(def) mutant cells with constitutive SOS-expression, a 10-fold increase in DNA breaks was observed. Inactivation of all 4 translesion polymerases in the lexA(def) mutant reduced the deletion rate 250-fold without any concomitant reduction in the amount of DNA breaks. Mutational inactivation of 3 endonucleases under LexA control, reduced the number of DNA breaks to the wild-type level in a lexA(def) mutant with a concomitant 50-fold reduction in deletion rate. These findings suggest that the translesion polymerases are not involved in forming the DNA breaks, but that they require them to stimulate deletion formation.
Place, publisher, year, edition, pages
2009. Vol. 106, no 25, 10248-10253 p.
bacteria, DNA homology, gene loss, RecA protein
Medical and Health Sciences
Research subject Evolutionary Genetics
IdentifiersURN: urn:nbn:se:uu:diva-111424DOI: 10.1073/pnas.0904389106ISI: 000267292200034OAI: oai:DiVA.org:uu-111424DiVA: diva2:281150