부산대학교 도서관

Mycobacterium abscessus causes severe disease in patients with cystic fibrosis. Little is known in M. abscessus about the roles of small regulatory RNAs (sRNA) in gene regulation. We show that the sRNA B11 controls gene expression and virulence-associated phenotypes in this pathogen. B11 deletion from the smooth strain ATCC_19977 produced a rough strain, increased pro-inflammatory signaling and virulence in multiple infection models, and increased resistance to antibiotics. Examination of clinical isolate cohorts identified isolates with B11 mutations or reduced expression. We used RNAseq and proteomics to investigate the effects of B11 on gene expression and test the impact of mutations found in clinical isolates. Over 200 genes were differentially expressed in the deletion mutant. Strains with the clinical B11 mutations showed expression trends similar to the deletion mutant, suggesting partial loss of function. Among genes upregulated in the B11 mutant, there was a strong enrichment for genes with B11-complementary sequences in their predicted ribosome binding sites (RBS), consistent with B11 functioning as a negative regulator that represses translation via base-pairing to RBSs. Comparing the proteomes similarly revealed that upregulated proteins were strongly enriched for B11-complementary sequences. Intriguingly, genes upregulated in the absence of B11 included components of the ESX-4 secretion system, critical for M. abscessus virulence. Many of these genes had B11-complementary sequences at their RBSs, which we show is sufficient to mediate repression by B11 through direct binding. Altogether, our data show that B11 acts as a direct negative regulator and mediates (likely indirect) positive regulation with pleiotropic effects on gene expression and clinically important phenotypes in M. abscessus. The presence of hypomorphic B11 mutations in clinical strains is consistent with the idea that lower B11 activity may be advantageous for M. abscessus in some clinical contexts. This is the first report on an sRNA role in M. abscessus. Author summary: Mycobacterium abscessus is a bacterial pathogen that causes difficult-to-treat disease. To develop better treatments for M. abscessus infections, we need to better understand how it adapts to the stresses imposed by antibiotics and the immune system. Bacteria, and specifically pathogens, need to regulate gene expression to control their physiology and virulence. In better studied bacteria, small non-coding RNAs (sRNAs) have been shown to participate in gene regulation. In contrast, almost nothing is known about the roles of sRNAs in M. abscessus. Here, we identified an sRNA in M. abscessus called B11 (also present in other mycobacterial pathogens) that is a pleotropic regulator of multiple pathways–both increasing and decreasing the expression of ~200 genes belonging to pivotal pathogenesis phenotypes. Deletion of B11 resulted in a hyper-inflammatory, hyper virulent strain, via altered expression of genes in multiple virulence pathways. We experimentally show that for some genes, the mechanistic basis for this regulation is direct binding of the sRNA to target mRNA via specific basepairing. It appears that deletion of B11 increases the virulence of the bacterium–and this notion is supported by the finding of B11 hypomorphic mutations in three unrelated cohorts of clinical isolates of M. abscessus. [ABSTRACT FROM AUTHOR]