The role of multiple SOS boxes upstream of the Mycobacterium tuberculosis lexA gene - identification of a novel DNA-damage-inducible gene

Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK 1 Author for correspondence: Elaine O. Davis. Tel: +44 20 8959 3666. Fax: +44 20 8913 8528. e-mail: edavis{at}nimr.mrc.ac.uk Four potential binding sites for LexA were identified upstream of the Mycobacterium tuberculosis lexA gene. A mutational analysis of these sites in a lexA – lacZ reporter construct revealed that only one of these SOS boxes was required for DNA-damage-mediated regulation of lexA expression. A novel DNA-damage-inducible gene, Rv2719c , was identified that was divergently transcribed relative to lexA ; the other three SOS boxes were found to be involved in regulating expression of this novel mycobacterial-specific gene. The SOS boxes lay in the respective promoter regions of the genes that they regulated. Keywords: LexA, SOS box, mycobacteria Abbreviations: RACE, rapid amplification of cDNA ends a Present address: The University of British Columbia, The Research Centre, Faculty of Medicine, Dept of Paediatrics, 950 West 28th Avenue, Vancouver, BC, Canada V5Z 4H4.