AbmR (Rv1265) is a novel transcription factor of Mycobacterium tuberculosis that regulates host cell association and expression of the non-coding small RNA Mcr11.
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ABSTRACT: Gene regulatory networks used by Mycobacterium tuberculosis (Mtb) during infection include many genes of unknown function, confounding efforts to determine their roles in Mtb biology. Rv1265 encodes a conserved hypothetical protein that is expressed during infection and in response to elevated levels of cyclic AMP. Here, we report that Rv1265 is a novel auto-inhibitory ATP-binding transcription factor that upregulates expression of the small non-coding RNA Mcr11, and propose that Rv1265 be named ATP-binding mcr11 regulator (AbmR). AbmR directly and specifically bound DNA, as determined by electrophoretic mobility shift assays, and this DNA-binding activity was enhanced by AbmR's interaction with ATP. Genetic knockout of abmR in Mtb increased abmR promoter activity and eliminated growth phase-dependent increases in mcr11 expression during hypoxia. Mutagenesis identified arginine residues in the carboxy terminus that are critical for AbmR's DNA-binding activity and gene regulatory function. Limited similarity to other DNA- or ATP-binding domains suggests that AbmR belongs to a novel class of DNA- and ATP-binding proteins. AbmR was also found to form large organized structures in solution and facilitate the serum-dependent association of Mtb with human lung epithelial cells. These results indicate a potentially complex role for AbmR in Mtb biology.
Project description:Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis, must adapt to host-associated environments during infection by modulating gene expression. Small regulatory RNAs (sRNAs) are key regulators of bacterial gene expression, but their roles in Mtb are not well understood. Here, we address the expression and function of the Mtb sRNA Mcr11, which is associated with slow bacterial growth and chronic infections in mice. We found that stable expression of Mcr11 requires multiple factors specific to TB-complex bacteria, including the AbmR transcription factor. Bioinformatic analyses used to predict regulatory targets of Mcr11 identified 7-11 nucleotide regions with potential for direct base-pairing with Mcr11 immediately upstream of Rv3282, fadA3, and lipB. mcr11-dependent regulation of these genes was demonstrated using qRT-PCR and found to be responsive to the presence of fatty acids. Mutation of the putative Mcr11 base-pairing site upstream of lipB in a promoter reporter strain resulted in significant de-repression of lipB expression, similar to that observed in mcr11-deleted Mtb. These studies establish Mcr11's roles in regulating growth and central metabolism in Mtb. Our finding that multiple TB-complex-specific factors are required for production of stable Mcr11 also emphasizes the need to better understand mechanisms of sRNA expression and stability in TB.
Project description:The interaction of Mycobacterium tuberculosis (Mtb) with host cell death signaling pathways is characterized by an initial anti-apoptotic phase followed by a pro-necrotic phase to allow for host cell exit of the bacteria. The bacterial modulators regulating necrosis induction are poorly understood. Here we describe the identification of a transcriptional repressor, Rv3167c responsible for regulating the escape of Mtb from the phagosome. Increased cytosolic localization of MtbΔRv3167c was accompanied by elevated levels of mitochondrial reactive oxygen species and reduced activation of the protein kinase Akt, and these events were critical for the induction of host cell necrosis and macroautophagy. The increase in necrosis led to an increase in bacterial virulence as reflected in higher bacterial burden and reduced survival of mice infected with MtbΔRv3167c. The regulon of Rv3167c thus contains the bacterial mediators involved in escape from the phagosome and host cell necrosis induction, both of which are crucial steps in the intracellular lifecycle and virulence of Mtb.
Project description:We report a study about differentially expressed small non-coding RNAs in the blood of humans harboring a latent (LTBI) or active tuberculosis (TB) infection in comparison with exposed controls (ExC) and treated LTBI (LTBItt). All non-TB subjects enrolled in this study were recent close contacts (rCt) of a newly diagnosed contagious TB cases enrolled in Rio de Janeiro, Brazil. The detailed methodology is described below. According to Brazilian Ministry of Health (BMH) guidelines, the screen to detect LTBI among recent contacts comprises a clinical evaluation by a physician specializing in pulmonary diseases, a chest X-ray (CXR), and a tuberculin skin test (TST, cut-off 5mm). Additionally, as part of this study, blood was collected for short- (st) and long-term (lt) IGRA. St-IGRA was performed by stimulating whole blood with the Mtb antigen ESAT6:CFP10 (expressed as a fusion protein) for 22h (cut-off 10pg/mL). Lt-IGRA involved stimulating peripheral blood mononuclear cells (PBMC) with this same antigen for 5 days (cut-off 100 pg/mL). Cases were defined as follows: ExC were recent close contacts of a TB index case and had a negative response to both TST and in house interferon-gamma release assay (IGRA) by stimulating blood-derived specimens with ESAT6:CFP10 indicating absence of Mycobacterium tuberculosis (Mtb) infection. LTBI was defined as (1) a TST induration >5 mm measured 72 h after intradermal injection of Mtb purified protein derivative (PPD) and (2) a positive IGRA response (to either st-IGRA or lt-IGRA, or both); if indicators of active disease were observed on CXR, (3) the absence of acid-fast bacilli (AFB) and negative Lowenstein-Jensen (LJ) culture of clinical specimens were also required. LTBItt consisted of LTBI cases (TST+/IGRA+ at enrollment) who completed a 6-month course of IPT. Their blood samples were collected >2 months after the end of isoniazid (INH) preventive treatment (IPT). Active TB was defined as (1) respiratory symptoms suggestive of TB, and/or (2) detection of AFB and/or positive LJ culture in sputum, bronchoalveolar lavage or biopsy, followed by (3) remission of symptoms upon anti-TB chemotherapy. Their blood samples were obtained before initiation of treatment. Whole blood was collected in PAXgene RNA tubes (PreAnalytiX, SWZ) and was stored at -80°C for <2 years before RNA extraction. sncRNA libraries. Total RNA (including small RNA) was isolated using the PAXgene Blood miRNA Kit (PreAnalytiX, SWZ), which is indicated for the isolation and purification of total RNA longer than 18 nucleotides. The manufacturer’s instructions were followed at both stages. Total RNA was quantified with a Nanodrop ND-1000 spectrophotometer (Thermo Scientific, EUA) and RNA integrity was assessed via agarose gel electrophoresis. One microgram RNA was used for cDNA library preparation (TruSeq Small RNA Sample Preparation® Kit, Illumina, San Diego, CA) following the manufacturer’s protocols. RNAseq was performed on an Illumina HiSeq® 2500 Sequencing System (Illumina, San Diego, CA), generating 50 bp single reads and ≈16 million reads passing filter for each sample. Pre-processing and differential expression. The FASTQ files were preprocessed (FastQC 0.11.2), adaptors trimmed (Cutadapt 1.7.1), aligned to the human genome (STAR 2.4.1d), counted (featureCounts 1.4.6) on the Oasis 2.0 web platform. Transcripts with <5 reads in at least one sample were excluded. Then, normalized and evaluated for differentially expressed (DE) transcripts using DESeq2 (v. 1.16) on the Oasis 2.0 web platform (https://oasis.dzne.de/).
Project description: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.
Project description:Bacterial pathogens trigger specialized virulence factor secretion systems on encountering host cells. The ESX-1 protein secretion system of Mycobacterium tuberculosis-the causative agent of the human disease tuberculosis-delivers bacterial proteins into host cells during infection and is critical for virulence, but how it is regulated is unknown. Here we show that EspR (also known as Rv3849) is a key regulator of ESX-1 that is required for secretion and virulence in mice. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. EspR directly binds to and activates the Rv3616c-Rv3614c promoter and, unexpectedly, is itself secreted from the bacterial cell by the ESX-1 system that it regulates. Efflux of the DNA-binding regulator results in reduced Rv3616c-Rv3614c transcription, and thus reduced ESX-1 secretion. Our results reveal a direct negative feedback loop that regulates the activity of a secretion system essential for virulence. As the virulence factors secreted by the ESX-1 system are highly antigenic, fine control of secretion may be critical to successful infection.
Project description:Development of host protective immunity against Mycobacterium tuberculosis infection is critically dependent on the inflammatory cytokine TNF. TNF signals through 2 receptors, TNFRp55 and TNFRp75; however, the role of TNFRp75-dependent signaling in immune regulation is poorly defined. Here we found that mice lacking TNFRp75 exhibit greater control of M. tuberculosis infection compared with WT mice. TNFRp75-/- mice developed effective bactericidal granulomas and demonstrated increased pulmonary recruitment of activated DCs. Moreover, IL-12p40-dependent migration of DCs to lung draining LNs of infected TNFRp75-/- mice was substantially higher than that observed in WT M. tuberculosis-infected animals and was associated with enhanced frequencies of activated M. tuberculosis-specific IFN-?-expressing CD4+ T cells. In WT mice, TNFRp75 shedding correlated with markedly reduced bioactive TNF levels and IL-12p40 expression. Neutralization of TNFRp75 in M. tuberculosis-infected WT BM-derived DCs (BMDCs) increased production of bioactive TNF and IL-12p40 to a level equivalent to that produced by TNFRp75-/- BMDCs. Addition of exogenous TNFRp75 to TNFRp75-/- BMDCs infected with M. tuberculosis decreased IL-12p40 synthesis, demonstrating that TNFRp75 shedding regulates DC activation. These data indicate that TNFRp75 shedding downmodulates protective immune function and reduces host resistance and survival; therefore, targeting TNFRp75 may be beneficial for improving disease outcome.
Project description:PurposeRecent studies have shown that long non-coding RNA (lncRNA) play an important role in cancer metabolism and development. The lncRNA small nucleolar RNA host gene 7 (SNHG7) was reported to be upregulated in colorectal cancer and contribute to its progression. In the current study, we investigated the role of lncRNA-SNHG7 in breast cancer and explored the underlying mechanism.MethodsWe monitored the expression of lncRNA-SNHG7 in breast cancer tissues and breast cancer cell lines. We evaluated the effects of lncRNA-SNHG7 on cell proliferation and glycolysis in breast cancer cells by knocking down or overexpressing lncRNA-SNHG7. We searched for the potential microRNA (miRNA) target of lncRNA-SNHG7 and evaluated the effects of the target miRNA on glycolysis. We evaluated the potential regulation of lncRNA-SNHG7 by c-Myc.ResultsLncRNA-SNHG7 was up-regulated in both breast cancer tissues and breast cancer cell lines. Knocking down lncRNA-SNHG7 inhibited breast cancer cell proliferation while overexpressing lncRNA-SNHG7 enhanced cell proliferation. Knocking down lncRNA-SNHG7 resulted in decreased expression of lactate dehydrogenase A (LDHA) and decreased glycolysis. LncRNA-SNHG7 targeted miR-34a-5p to regulate LDHA expression and glycolysis. c-Myc bound to promoter of lncRNA-SNHG7 and positively regulated lncRNA-SNHG7 expression.ConclusionWe demonstrated that c-Myc regulated glycolysis through the lncRNA-SNHG7/miR-34a-5p/LDHA axis in breast cancer cells.
Project description:Small non-coding RNAs play a significant role in bacterial adaptation to changing environmental conditions. We investigated the dynamics of expression of MTS1338, a small non-coding RNA of Mycobacterium tuberculosis, in the mouse model in vivo, regulation of its expression in the infected macrophages, and the consequences of its overexpression in bacterial cultures. Here we demonstrate that MTS1338 significantly contributes to host-pathogen interactions. Activation of the host immune system triggered NO-inducible up-regulation of MTS1338 in macrophage-engulfed mycobacteria. Constitutive overexpression of MTS1338 in cultured mycobacteria improved their survival in vitro under low pH conditions. MTS1338 up-regulation launched a spectrum of shifts in the transcriptome profile similar to those reported for M. tuberculosis adaptation to hostile intra-macrophage environment. Using the RNA-seq approach, we demonstrate that gene expression changes accompanying MTS1338 overexpression indicate reduction in translational activity and bacterial growth. These changes indicate mycobacteria entering the dormant state. Taken together, our results suggest a direct involvement of this sRNA in the interplay between mycobacteria and the host immune system during infectious process.
Project description:BackgroundMembers of the WhiB-like (Wbl) protein family possess iron-sulfur clusters and are implicated in the regulation of developmental processes in Actinomycetes. Mycobacterium tuberculosis possesses seven Wbl proteins. The [4Fe-4S] cluster of M. tuberculosis WhiB1 is relatively insensitive to O(2) but very sensitive to nitric oxide (NO). Nitric oxide nitrosylates the WhiB1 iron-sulfur cluster and promotes DNA-binding; the apo-forms of WhiB1 also bind DNA. However, the molecular requirements for iron-sulfur cluster acquisition and for DNA-binding by WhiB1 are poorly characterized.Methods and findingsWhiB1 variants were created by site-directed mutagenesis and the abilities of the corresponding proteins to acquire an iron-sulfur cluster and/or bind to whiB1 promoter DNA were assessed. All four Cys residues (Cys9, 37, 40, and 46) in the N-terminal region of WhiB1 were required for incorporation of a [4Fe-4S] cluster, whereas a possible alternative cluster ligand Asp13 (by analogy with M. smegmatis WhiB2) was not. The C-terminal region of WhiB1 is predicted to house the DNA-binding domain of the protein consisting of a predicted β-turn ((58)GVWGG(62)) followed by two amino acid motifs ((72)KRRN(75) and (78)TKAR(81)) that are conserved in WhiB1 proteins. Gly residues (Gly58, 61 and 62) in the β-turn and positively-charged residues (Lys72, Arg73, Arg74, Lys79 and Arg81) in the downstream conserved regions were required for binding of WhiB1 DNA.ConclusionsSite-directed mutagenesis of M. tuberculosis whiB1 and characterization of the corresponding proteins has been used to explore structure-function relationships of the NO-responsive transcription factor WhiB1. This showed that all four conserved Cys residues in the N-terminal region are required for incorporation of iron-sulfur clusters but not for DNA-binding. Analysis of variants with amino acid substitutions in the C-terminal region revealed the crucial roles played by a predicted β-turn and two conserved positively-charged motifs in facilitating DNA-binding, but not iron-sulfur cluster acquisition, by WhiB1.