title: Specific mutations in the Mycobacterium tuberculosis rpoB gene are associated with increased dnaE2 expression.
abstract: In Mycobacterium tuberculosis (MTB), rifampicin resistance is almost invariably due to mutations in the rpoB gene, whose function is critical for cell viability. Most of these mutations, at least initially, impair the fitness of the bacteria but confer a selective advantage when antibiotic pressure is exerted. Subsequent adaptation may be critical to restore fitness. The possibility was considered that MTB with mutations in the rpoB gene elicits a constitutive stress response, increasing the probability of subsequent adaptation. In order to test this hypothesis, the expression of recA and dnaE2, an inducible putative error-prone DNA polymerase, was determined in six different isogenic laboratory-generated rpoB-mutants of MTB. Expression levels were determined with real-time PCR and the data obtained were compared with those of the wild-type parent. In four of the six rpoB mutants, a two- to fivefold induction of dnaE2 was detected (P<0.05). Thus, the presence of specific mutations in rpoB is not only associated with impaired fitness but also results in a detectable, moderate yet persistent increase in the expression of dnaE2 but not recA.
authors.affiliation: Royal Tropical Institute, KIT Biomedical Research, Meibergdreef, Amsterdam, The Netherlands.
authors.forename: Indra L
authors.initials: IL
authors.lastname: Bergval
authors.forename: Paul R
authors.initials: PR
authors.lastname: Klatser
authors.forename: Anja R J
authors.initials: AR
authors.lastname: Schuitema
authors.forename: Linda
authors.initials: L
authors.lastname: Oskam
authors.forename: Richard M
authors.initials: RM
authors.lastname: Anthony
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003470:Culture Media; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases; D019020:Directed Molecular Evolution; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; C505805:rpoB protein, Mycobacterium tuberculosis; C074904:DNA polymerase III, alpha subunit; D012321:DNA-Directed RNA Polymerases; D004258:DNA Polymerase III