Lsr2, a pleiotropic regulator at the core of the infectious strategy ofMycobacterium abscessus

Abstract

ABSTRACTMycobacterium abscessusis a non-tuberculous mycobacterium, causing lung infections in cystic fibrosis patients. During pulmonary infection,M. abscessusswitches from smooth (Mabs-S) to rough (Mabs-R) morphotypes, the latter being hyper-virulent. Previously, we isolated thelsr2gene as differentially expressed during S-to-R transition.lsr2encodes a pleiotropic transcription factor that falls under the superfamily of nucleoid-associated proteins (NAPs). Here, we used two functional genomics methods, RNA-seq and ChIP-seq, to elucidate the molecular role of Lsr2 in the pathobiology ofM. abscessus. Transcriptomic analysis shows that Lsr2 differentially regulates gene expression across both morphotypes, most of which are involved in several key cellular processes ofM. abscessus, including host adaptation and antibiotic resistance. These results were confirmed through RT-qPCR, as well as by minimum inhibitory concentration (MIC) tests and infection tests on macrophages in the presence of antibiotics. ChIP-seq analysis revealed that Lsr2 extensively binds theM. abscessusgenome at AT-rich sequences and appears to form long domains that participate in the repression of its target genes. Unexpectedly, the genomic distribution of Lsr2 revealed no distinctions between Mabs-S and Mabs-R, implying more intricate mechanisms at play for achieving target selectivity.IMPORTANCELsr2 is a crucial transcription factor and chromosome organizer involved in intracellular growth and virulence in the smooth and rough morphotypes ofMycobacterium abscessus(Mabs). Using RNA-seq and ChIP-seq, we investigated the molecular role of Lsr2 in gene expression regulation along with its distribution on Mabs genome. Our study demonstrates the pleiotropic regulatory role of Lsr2, regulating the expression of many genes coordinating essential cellular and molecular processes in both morphotypes. In addition, we have elucidated the role of Lsr2 in antibiotic resistance bothin vitroandin vivo, wherelsr2mutant strains display heightened sensitivity to antibiotics. Through ChIP-seq, we reported the widespread distribution of Lsr2 on Mabs genome, revealing a direct repressive effect due to its extensive binding on promoters or coding sequences of its targets. This study unveils the significant regulatory role of Lsr2, intricately intertwined with its function in shaping the organization of the Mabs genome.