A stationary-phase stress-response sigma factor from Mycobacterium tuberculosis.
Alternative RNA polymerase sigma factors are a common means of coordinating gene regulation in bacteria. Using PCR amplification with degenerate primers, we identified and cloned a sigma factor gene, sigF, from Mycobacterium tuberculosis. The deduced protein encoded by sigF shows significant similarity to SigF sporulation sigma factors from Streptomyces coelicolor and Bacillus subtilis and to SigB, a stress-response sigma factor, from B. subtilis. Southern blot surveys with a sigF-specific probe identified cross-hybridizing bands in other slow-growing mycobacteria, Mycobacterium bovis bacille Calmette-Guérin (BCG) and Mycobacterium avium, but not in the rapid-growers Mycobacterium smegmatis or Mycobacterium abscessus. RNase protection assays revealed that M. tuberculosis sigF mRNA is not present during exponential-phase growth in M. bovis BCG cultures but is strongly induced during stationary phase, nitrogen depletion, and cold shock. Weak expression of M. tuberculosis sigF was also detected during late-exponential phase, oxidative stress, anaerobiasis, and alcohol shock. The specific expression of M. tuberculosis sigF during stress or stationary phase suggests that it may play a role in the ability of tubercle bacilli to adapt to host defenses and persist during human infection.
DeMaio
J
J
Department of Molecular Microbiology and Immunology, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205, USA.
Zhang
Y
Y
Ko
C
C
Young
D B
DB
Bishai
W R
WR
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics; D001483:Base Sequence; D017931:DNA Primers; D006801:Humans; D008969:Molecular Sequence Data; D009163:Mycobacterium bovis / Q000235:genetics / Q000502:physiology; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D018384:Oxidative Stress; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D013302:Streptomyces / Q000235:genetics
D017931:DNA Primers; D012333:RNA, Messenger; D012808:Sigma Factor