1. Interdepartmental Honours in Immunology project Activating Antigen Expression: In search of the stimulus for RskA By François Coulombe Marcel Behr’s laboratory October 19 2006

2. Mycobacterium tuberculosis Member of the MTC and causative agent of TB in humans Ability to survive and replicate within macrophages –Variety of virulence and adaptive genes under the control transcriptional regulators Alternative Sigma Factors Anti-Sigma Factors

3. Differential expression of mpt70/83 across the MTC mpt70/83 expression Low in vitro, high in vivo High in vitro, high in vivo? Low in vitro, low in vivo??? Humans Animals Vaccine

4. Hypothesis: A host factor is responsible for establishing a specific biochemical triggering condition or to interact directly with RskA (anti-SigK) leading to the release (i.e. activation) of SigK. C N RNA pol Inducing cues Inactive  Active  KK Expression of  K regulon: mpt70, dipZ, mpt83 KK Charlet et al., 2005 Saïd-Salim et al., in press M. tuberculosis cytoplasm Extracellular env. RskA

5. Experimental Strategies Ex vivo studies based on differential expression of mpt70/83 across MTC M. tuberculosis H37Ra (Wild-type, inducible expression) BCG Russia (Mutant RskA, constitutive high expression) BCG Pasteur (Mutant SigK, constitutive low expression) –Intracellular mycobacterial RNA extraction from THP-1 cells –Protein-protein interaction assay (e.g. yeast-two hybrid) –Decomposition of THP-1 cells infection

6. Acknowledgements Supervisor: Dr. Marcel Behr Dr. Arnold Kristof Frédéric Veyrier, Battouli Saïd-Salim, Serge Mostowy and all members of the Behr lab. Dr. Erwin Schurr laboratory members See you in January…!