title: Sigma factor F does not prevent rifampin inhibition of RNA polymerase or cause rifampin tolerance in Mycobacterium tuberculosis.
abstract: The tolerance of Mycobacterium tuberculosis to antituberculosis drugs is a major reason for the lengthy therapy needed to treat a tuberculosis infection. Rifampin is a potent inhibitor of RNA polymerase (RNAP) in vivo but has been shown to be less effective against stationary-phase bacteria. Sigma factor F is associated with bacteria entering stationary phase and has been proposed to impact rifampin activity. Here we investigate whether RNAP containing SigF is more resistant to rifampin inhibition in vitro and whether overexpression of sigF renders M. tuberculosis more tolerant to rifampin. Real-time and radiometric in vitro transcription assays revealed that rifampin equally inhibits transcription by RNAP containing sigma factors SigA and SigF, therefore ruling out the hypothesis that SigF may be responsible for increased resistance of the enzyme to rifampin in vitro. In addition, overexpression or deletion of sigF did not alter rifampin susceptibility in axenic cultures of M. tuberculosis, indicating that SigF does not affect rifampin tolerance in vivo.
authors: Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland. ruben.hartkoorn@epfl.ch
authors: Ruben C
authors: RC
authors: Hartkoorn
authors: Claudia
authors: C
authors: Sala
authors: Sophie J
authors: SJ
authors: Magnet
authors: Jeffrey M
authors: JM
authors: Chen
authors: Florence
authors: F
authors: Pojer
authors: Stewart T
authors: ST
authors: Cole
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors*; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000378:metabolism; D009499:Neutral Red; D011994:Recombinant Proteins; D012293:Rifampin / Q000494:pharmacology*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013194:Staining and Labeling; D025381:Streptogramin B / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C064971:FliA protein, Bacteria; D011994:Recombinant Proteins; D012808:Sigma Factor; D009499:Neutral Red; D025381:Streptogramin B; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin