Mutation of a multiple antibiotic resistance (mar) gene confers Mycobacterium tuberculosis resistance to a pyrido[1,2-a]benzimidazole-based agent. Mycobacterium tuberculosis H37Rv

Drug resistance is major problem in Mycobacterium tuberculosis control, and it is critical to identify novel drug targets and new anti-mycobacterial compounds. We have previously identified a pyrido[1,2-a]benzimidazole-based agent, MP-III-71, with strong activity against M. tuberculosis. Here, we sequenced three mutants resistant to MP-III-71 and found that mutations in Rv2887 confer resistance to MP-III-71, which we confirmed through complementation. This protein was previously un-annotated, but domain and homology analysis suggested that Rv2887 encodes a putative transcriptional regulator in the MarR (multiple antibiotic resistance repressor) family, a group of proteins first identified in E. coli to negatively regulate efflux pumps and other mechanisms of multi-drug resistance. We next determined the regulon of Rv2887 through RNA-seq. One of the genes downregulated by Rv887 is Rv2463, a putative MarA transcriptional activator. The putative regulon also includes genes involved in benzoquinone and menaquinone biosynthesis. Thus, mutation of Rv2887, a transcriptional regulator, confers resistance to MP-III-71, an effective anti-mycobacterial compound that shows no cross-resistance to existing anti-tuberculosis drugs, and thus could be an effective target in drug-resistant strains of M. tuberculosis.