A novel mechanism of rifamycin resistance in Mycobacterium abscessus mediated by a putative helicase

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Project Summary: Mycobacterium abscessus (Mab) is a rapidly growing NTM causing skin and soft tissue infections as well as pulmonary infections in patients with chronic lung damage. Mab stands apart as one of the most antibiotic resistant microbial species, making its infections incredibly difficult to treat. Particularly striking is its resistance to rifampicin (RIF), a frontline drug for many mycobacterial infections including tuberculosis. RIF inhibits global RNA synthesis by binding to the b-subunit of bacterial RNA polymerase; additionally it is also known to inhibit replication initiation due to an inhibition of dnaA expression. The intrinsic RIF resistance in Mab has so far been attributed to the presence of an ADP-ribosyltransferase (Arr) activity that ribosylates RIF leading to its inactivation. However, we have recently identified an additional determinant, MAB_3189c - a putative helicase, that confers high levels of RIF resistance in Mab. MAB_3189c expression is RIF inducible and is likely regulated by a RIF-associated element (RAE) dependent transcription factor. In this project we will determine the regulation and function of Mab3189c in RIF resistance. In Aim 1 we will investigate if Mab3189c mediates RIF resistance by either directly protecting RNAP against the action of RIF thereby enabling global RNA synthesis to continue, or by alleviating RIF-sensitive replication initiation at oriM thereby enabling growth in the presence of RIF. In Aim 2 we propose to identify the regulatory protein required for RAE-dependent induction of MAB_3189c. The findings will provide a platform for a long-term study to gain insights into Mab3189c dependent RIF resistance in Mab, and design of new strategies to treat Mab infections.