AUTHOR=Perrone Filomena , De Siena Barbara , Muscariello Lidia , Kendall Sharon L. , Waddell Simon J. , Sacco Margherita 

TITLE=A Novel TetR-Like Transcriptional Regulator Is Induced in Acid-Nitrosative Stress and Controls Expression of an Efflux Pump in Mycobacteria

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02039

DOI=10.3389/fmicb.2017.02039

ISSN=1664-302X

ABSTRACT=<p><italic>Mycobacterium tuberculosis</italic> has the ability to survive inside macrophages under acid-nitrosative stress. <italic>M. tuberculosis Rv1685c</italic> and its ortholog in <italic>M. smegmatis, MSMEG_3765</italic>, are induced on exposure to acid-nitrosative stress. Both genes are annotated as TetR transcriptional regulators, a family of proteins that regulate a wide range of cellular activities, including multidrug resistance, carbon catabolism and virulence. Here, we demonstrate that <italic>MSMEG_3765</italic> is co-transcribed with the upstream genes <italic>MSMEG_3762</italic> and <italic>MSMEG_3763</italic>, encoding efflux pump components. RTq-PCR and GFP-reporter assays showed that the <italic>MSMEG_3762/63/65</italic> gene cluster, and the orthologous region in <italic>M. tuberculosis</italic> (<italic>Rv1687c/86c/85c</italic>), was up-regulated in a <italic>MSMEG_3765</italic> null mutant, suggesting that <italic>MSMEG_3765</italic> acts as a repressor, typical of this family of regulators. We further defined the <italic>MSMEG_3765</italic> regulon using genome-wide transcriptional profiling and used reporter assays to confirm that the <italic>MSMEG_3762/63/65</italic> promoter was induced under acid-nitrosative stress. A putative 36 bp regulatory motif was identified upstream of the gene clusters in both <italic>M. smegmatis</italic> and <italic>M. tuberculosis</italic> and purified recombinant MSMEG_3765 protein was found to bind to DNA fragments containing this motif from both <italic>M. smegmatis</italic> and <italic>M. tuberculosis</italic> upstream regulatory regions. These results suggest that the TetR repressor <italic>MSMEG_3765/Rv1685c</italic> controls expression of an efflux pump with an, as yet, undefined role in the mycobacterial response to acid-nitrosative stress.</p>