A Stationary-Phase Stress-Response Sigma Factor from Mycobacterium tuberculosis

• Published in: Proceedings of the National Academy of Sciences - PNAS 1996-04, Vol.93 (7), p.2790-2794
• Main Authors: DeMaio, James, Zhang, Ying, Ko, Chiew, Young, Douglas B., Bishai, William R.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacillus subtilis - genetics; Bacteria; Base Sequence; Culture shock; DNA; DNA Primers; Genes; Genetics; Humans; Messenger RNA; Molecular Sequence Data; Mycobacterium bovis - genetics; Mycobacterium bovis - physiology; Mycobacterium tuberculosis; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - growth & development; Mycobacterium tuberculosis - physiology; Oxidative Stress; Polymerase Chain Reaction; Restriction Mapping; Ribonucleic acid; RNA; RNA, Messenger - analysis; RNA, Messenger - biosynthesis; Sequence Homology, Amino Acid; Sigma Factor - biosynthesis; Sigma Factor - chemistry; Sigma Factor - genetics; Sporulation; Steepest descent method; Streptomyces - genetics; Tuberculosis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.7.2790

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-Guerin (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.