The mechanism of upstream activation in the rrnB operon of Mycobacterium smegmatis is different from the Escherichia coli paradigm

• Published in: Microbiology (Society for General Microbiology) 2005-02, Vol.151 (2), p.467-473
• Main Authors: Arnvig, Kristine B, Gopal, B, Papavinasasundaram, K. G, Cox, Robert A, Colston, M. Joseph
• Format: Article
• Language: English
• Subjects: Bacteriology; Base Sequence; Biological and medical sciences; DNA, Bacterial - analysis; DNA, Bacterial - genetics; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Microbiology; Miscellaneous; Molecular Sequence Data; Mycobacterium smegmatis; Mycobacterium smegmatis - genetics; Mycobacterium smegmatis - metabolism; Promoter Regions, Genetic - genetics; rRNA Operon - genetics; rRNA Operon - physiology; Species Specificity; Transcription, Genetic
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.27597-0

1 Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK 2 Division of Protein Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK Correspondence Kristine B. Arnvig karnvig{at}nimr.mrc.ac.uk Mycobacteria are slow-growing bacteria with a generation time of from 2–3 h up to several weeks. Consistent with the low growth rate, mycobacterial species have a maximum of two rRNA operons, rrnA and rrnB . The rrnA operon is present in all mycobacteria and has between two and five promoters, depending on species, whereas the rrnB operon, with a single promoter, is only found in some of the faster-growing species. The promoter region of the rrnB operon of a typical fast grower, Mycobacterium smegmatis , was investigated. By using lacZ reporter gene fusions it was demonstrated that the rrnB operon contains a highly activating region upstream of the core promoter, comparable to other bacterial rrn operons. However, the results suggest that, unlike the situation in, for example, Escherichia coli , the activating mechanism is solely factor dependent, and that no UP element is involved. Abbreviations: CTD, C-terminal domain; EMSA, electrophoretic mobility shift assays; -gal, -galactosidase; RNAP , RNA polymerase alpha subunit; UAR, upstream activating region; UR, upstream region * Present address: Indian Institute of Science, Bangalore 560012, India. Present address: Department of Medicine, Division of Infectious Diseases, University of British Columbia, Vancouver, Canada V5Z 3J5. Deceased 20 February 2003.