title: Slow induction of RecA by DNA damage in Mycobacterium tuberculosis.
abstract: In mycobacteria, as in most bacterial species, the expression of RecA is induced by DNA damage. However, the authors show here that the kinetics of recA induction in Mycobacterium smegmatis and in Mycobacterium tuberculosis are quite different: whilst maximum expression in M. smegmatis occurred 3-6 h after addition of a DNA-damaging agent, incubation for 18-36 h was required to reach peak levels in M. tuberculosis. This is despite the fact that the M. tuberculosis promoter can be activated more rapidly when transferred to M. smegmatis. In addition, it is demonstrated that in both species the DNA is sufficiently damaged to give maximum induction within the first hour of incubation with mitomycin C. The difference in the induction kinetics of recA between the two species was mirrored by a difference in the levels of DNA-binding-competent LexA following DNA damage. A decrease in the ability of LexA to bind to the SOS box was readily detected by 2 h in M. smegmatis, whilst a decrease was not apparent until 18-24 h in M. tuberculosis and then only a very small decrease was observed.
authors.affiliation: Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK. kpapavi@nimr.mrc.ac.uk
authors.forename: K G
authors.initials: KG
authors.lastname: Papavinasasundaram
authors.forename: C
authors.initials: C
authors.lastname: Anderson
authors.forename: P C
authors.initials: PC
authors.lastname: Brooks
authors.forename: N A
authors.initials: NA
authors.lastname: Thomas
authors.forename: F
authors.initials: F
authors.lastname: Movahedzadeh
authors.forename: P J
authors.initials: PJ
authors.lastname: Jenner
authors.forename: M J
authors.initials: MJ
authors.lastname: Colston
authors.forename: E O
authors.initials: EO
authors.lastname: Davis
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics*; D004790:Enzyme Induction; D015964:Gene Expression Regulation, Bacterial; D016685:Mitomycin / Q000494:pharmacology; D020102:Mycobacterium smegmatis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011938:Rec A Recombinases / Q000096:biosynthesis / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D013045:Species Specificity; D000099160:LexA Repressor Protein
chemical_list: D000477:Alkylating Agents; D001426:Bacterial Proteins; D016685:Mitomycin; D011938:Rec A Recombinases; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein