Noncoding RNA in Mycobacteria

RegX3-dependent transcriptional activation of kdpDE and repression of rv0500A are linked to potassium homeostasis in Mycobacterium tuberculosis

Ionic homeostasis is essential for the survival and replication of Mycobacterium tuberculosis within its host. Low potassium ion concentrations trigger a transition of M. tuberculosis into dormancy. Our current knowledge of the transcriptional regulation mechanisms governing genes involved in potassium homeostasis remains limited. Potassium transport is regulated by the constitutive Trk system and the inducible Kdp system in M. tuberculosis. The two-component system KdpDE (also known as KdpD/KdpE) activates expression of the kdpFABC operon, encoding the four protein subunits of the Kdp potassium uptake system (KdpFABC). We show that, under potassium deficiency, expression of the two-component system senX3/regX3 is upregulated, and bacterial survival is compromised in a regX3-inactivated mutant, ΔregX3. Electrophoretic mobility shift assays (EMSAs), promoter reporter assays and chromatin immunoprecipitation (ChIP) show that RegX3 binds to the kdpDE promoter and activates it under potassium deficiency, whereas RegX3 (K204A), a DNA binding-deficient mutant, fails to bind to the promoter. Mutation of the RegX3 binding motifs on the kdpDE promoter abrogates RegX3 binding. In addition, EMSAs and ChIP assays show that RegX3 represses Rv0500A, a repressor of kdpFABC, by binding to consensus RegX3 binding motifs on the rv0500A promoter. Our findings provide important insight into two converging pathways regulated by RegX3; one in which it activates an activator of kdpFABC, and the other in which it represses a repressor of kdpFABC, during potassium insufficiency. This culminates in increased expression of the potassium uptake system encoded by kdpFABC, enabling bacterial survival. These results further expand the growing transcriptional network in which RegX3 serves as a central node to enable bacterial survival under stress.

LncRNA MIR503HG promotes hypertrophic scar progression via miR-143-3p-mediated Smad3 expression

Hypertrophic scars (HSs) form due to unchecked proliferation of fibrous tissue after an injury to the skin. Recently, lncRNA MIR503HG was shown to be involved in HS. However, the mechanism by which MIR503HG affects the formation and progression of HS still needs further study. qRT-PCR was applied to examine the levels of MIR503HG and miR-143-3p in HS tissues and human hypertrophic scar fibroblasts (hHSFs). The relationships of MIR503HG, miR-143-3p and Smad3 were explored with a dual-luciferase reporter assay. Cell proliferation, apoptosis, and invasion were measured by CCK-8 assay, flow cytometry and transwell assay, respectively. The protein level of Smad3 was tested via Western blotting. MIR503HG was upregulated and miR-143-3p was downregulated in HS versus normal skin tissues. The knockdown of MIR503HG and the overexpression of miR-143-3p suppressed the proliferation and invasion of hHSF, and promoted cell apoptosis. MIR503HG bound to miR-143-3p while miR-143-3p directly targeted Smad3 to inhibit its expression. Suppression of miR-143-3p and overexpression of Smad3, respectively, reversed these effects of knockdown of MIR503HG and overexpression of miR-143-3p on hHSFs. Our research supports a model in which the MIR503HG/miR-143-3p/Smad3 axis serves as a critical regulator of HS, highlighting a promising therapeutic option for HS.

Regulatory networks between Polycomb complexes and non-coding RNAs in the central nervous system

High-throughput sequencing has facilitated the identification of many types of non-coding RNAs (ncRNAs) involved in diverse cellular processes. NcRNAs as epigenetic mediators play key roles in neuronal development, maintenance, and dysfunction by controlling gene expression at multiple levels. NcRNAs may not only target specific DNA or RNA for gene silence but may also directly interact with chromatin-modifying proteins like Polycomb group (PcG) proteins to drive orchestrated transcriptional programs. Recent significant progress has been made in characterizing ncRNAs and PcG proteins involved in transcriptional, post-transcriptional, and epigenetic regulation. More importantly, dysregulation of ncRNAs, PcG proteins, and interplay among them is closely associated with the pathogenesis of central nervous system (CNS) disorders. In this review, we focus on the interplay between ncRNAs and PcG proteins in the CNS and highlight the functional roles of the partnership during neural development and diseases.

Transposon mutagenesis in Mycobacterium kansasii links a small RNA gene to colony morphology and biofilm formation and identifies 9,885 intragenic insertions that do not compromise colony outgrowth

Mycobacterium kansasii (Mk) is a resilient opportunistic human pathogen that causes tuberculosis‐like chronic pulmonary disease and mortality stemming from comorbidities and treatment failure. The standard treatment of Mk infections requires costly, long‐term, multidrug courses with adverse side effects. The emergence of drug‐resistant isolates further complicates the already challenging drug therapy regimens and threatens to compromise the future control of Mk infections. Despite the increasingly recognized global burden of Mk infections, the biology of this opportunistic pathogen remains essentially unexplored. In particular, studies reporting gene function or generation of defined mutants are scarce. Moreover, no transposon (Tn) mutagenesis tool has been validated for use in Mk, a situation limiting the repertoire of genetic approaches available to accelerate the dissection of gene function and the generation of gene knockout mutants in this poorly characterized pathogen. In this study, we validated the functionality of a powerful Tn mutagenesis tool in Mk and used this tool in conjunction with a forward genetic screen to establish a previously unrecognized role of a conserved mycobacterial small RNA gene of unknown function in colony morphology features and biofilm formation. We also combined Tn mutagenesis with next‐generation sequencing to identify 12,071 Tn insertions that do not compromise viability in vitro. Finally, we demonstrated the susceptibility of the Galleria mellonella larva to Mk, setting the stage for further exploration of this simple and economical infection model system to the study of this pathogen.

Circular RNAs: epigenetic regulators in cancerous and noncancerous skin diseases

The most frequent kind of malignancy in the universe is skin cancer, which has been categorized into non-melanoma and melanoma skin cancer. There are no complete information of the skin carcinogenesis process. A variety of external and internal agents contribute to the non-melanoma and melanoma skin cancer pathogenesis. These factors are epigenetic changes, X-rays, genetic, arsenic compounds, UV rays, and additional chemical products. It was found that there could be a relationship between the appearing novel and more suitable therapies for participants in this class of diseases and detection of basic molecular paths. A covalently closed loop structure bond connecting the 5' and 3' ends characterizes a new group of extensively expressed endogenous regulatory RNAs, which are called circular RNAs (circRNAs). Mammals commonly express circRNAs. They are of high importance in tumorigenesis. Multiple lines evidence indicated that a variety of circular RNAs are associated with initiation and development of skin-related diseases such as skin cancers. Given that different circular RNAs (hsa_circ_0025039, hsa_circRNA006612, circRNA005537, and circANRIL) via targeting various cellular and molecular targets (e.g., CDK4, DAB2IP, ZEB1, miR-889, and let-7c-3p) exert their effects on skin cancers progression. Herein, for first time, we summarized different circular RNAs in skin cancers and noncancerous diseases. Moreover, we highlighted crosstalk between circular RNAs and ceRNAs in cancerous conditions.

Comparative genomics of Mycobacterium mucogenicum and Mycobacterium neoaurum clade members emphasizing tRNA and non-coding RNA

Background

Mycobacteria occupy various ecological niches and can be isolated from soil, tap water and ground water. Several cause diseases in humans and animals. To get deeper insight into our understanding of mycobacterial evolution focusing on tRNA and non-coding (nc)RNA, we conducted a comparative genome analysis of Mycobacterium mucogenicum (Mmuc) and Mycobacterium neoaurum (Mneo) clade members.

Results

Genome sizes for Mmuc- and Mneo-clade members vary between 5.4 and 6.5 Mbps with the complete Mmuc^T (type strain) genome encompassing 6.1 Mbp. The number of tRNA genes range between 46 and 79 (including one pseudo tRNA gene) with 39 tRNA genes common among the members of these clades, while additional tRNA genes were probably acquired through horizontal gene transfer. Selected tRNAs and ncRNAs (RNase P RNA, tmRNA, 4.5S RNA, Ms1 RNA and 6C RNA) are expressed, and the levels for several of these are higher in stationary phase compared to exponentially growing cells. The rare tRNA^IleTAT isoacceptor and two for mycobacteria novel ncRNAs: the Lactobacillales-derived GOLLD RNA and a homolog to the antisense Salmonella typhimurium phage Sar RNA, were shown to be present and expressed in certain Mmuc-clade members.

Conclusions

Phages, IS elements, horizontally transferred tRNA gene clusters, and phage-derived ncRNAs appears to have influenced the evolution of the Mmuc- and Mneo-clades. While the number of predicted coding sequences correlates with genome size, the number of tRNA coding genes does not. The majority of the tRNA genes in mycobacteria are transcribed mainly from single genes and the levels of certain ncRNAs, including RNase P RNA (essential for the processing of tRNAs), are higher at stationary phase compared to exponentially growing cells. We provide supporting evidence that Ms1 RNA represents a mycobacterial 6S RNA variant. The evolutionary routes for the ncRNAs RNase P RNA, tmRNA and Ms1 RNA are different from that of the core genes.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1447-7) contains supplementary material, which is available to authorized users.

Bacterial Small RNAs in the Genus Herbaspirillum spp

The genus Herbaspirillum includes several strains isolated from different grasses. The identification of non-coding RNAs (ncRNAs) in the genus Herbaspirillum is an important stage studying the interaction of these molecules and the way they modulate physiological responses of different mechanisms, through RNA⁻RNA interaction or RNA⁻protein interaction. This interaction with their target occurs through the perfect pairing of short sequences (cis-encoded ncRNAs) or by the partial pairing of short sequences (trans-encoded ncRNAs). However, the companion Hfq can stabilize interactions in the trans-acting class. In addition, there are Riboswitches, located at the 5' end of mRNA and less often at the 3' end, which respond to environmental signals, high temperatures, or small binder molecules. Recently, CRISPR (clustered regularly interspaced palindromic repeats), in prokaryotes, have been described that consist of serial repeats of base sequences (spacer DNA) resulting from a previous exposure to exogenous plasmids or bacteriophages. We identified 285 ncRNAs in Herbaspirillum seropedicae (H. seropedicae) SmR1, expressed in different experimental conditions of RNA-seq material, classified as cis-encoded ncRNAs or trans-encoded ncRNAs and detected RNA riboswitch domains and CRISPR sequences. The results provide a better understanding of the participation of this type of RNA in the regulation of the metabolism of bacteria of the genus Herbaspirillum spp.

Uncloaking an ancient adversary: Can pathogen biomarker elicitors play a role in confirming extrapulmonary TB and latent TB infection?

Latent tuberculosis infection (LTBI) is diagnosed immunologically using the Mantoux tuberculin skin test (TST) or interferon-gamma release assays (IGRAs). While widely used, immunodiagnostics can produce false negative or false positive results. Pathogen biomarkers provide an alternative, but direct detection in LTBI and extrapulmonary TB cases is challenging. Mycobacterium tuberculosis grows slowly, has limited hematogenous movement, is protected by a lipid rich cell wall, and produces low levels of secreted factors. Here we discuss the potential of elicitors by first considering pathogen markers that may be released following the administration of isoniazid. Isoniazid targets the cell wall of mycobacteria found in extracellular compartments and within monocytes, macrophages, dendritic cells, and lymphatic endothelial cells. Isoniazid's dual-purpose potential as an antibiotic and elicitor is supported by knowledge of latent infection dynamics, time-kill kinetics, and new detection techniques. Within hours, the bactericidal action of isoniazid likely enriches plasma with M. tuberculosis DNA, RNA, proteins/peptides, and lipids. Undoubtedly a portion of these biomarkers are eliminated as some bacilli undergo phagocytosis and lysosomal destruction. However, advances in immunoprecipitation and nucleic acid amplification, combined with the use of larger blood volumes during assay development, may overcome these losses. Other anticipated challenges include determining optimal sample collection times and designing diagnostic workflows that minimize processing-associated marker loss and degradation. Conventional, commercial, and emerging technologies that address these variables are discussed. If realized, isoniazid associated markers could provide proof of concept for novel elicitor-based diagnostic approaches capable of confirming LTBI and empirically treated extrapulmonary TB.

High‑throughput sequencing reveals differentially expressed lncRNAs and circRNAs, and their associated functional network, in human hypertrophic scars

Growing evidence suggests that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) are involved in the occurrence and development of tumors and fibrotic diseases. However, the integrated analysis of lncRNA and circRNA expression, alongside associated co-expression and competing endogenous RNA (ceRNA) networks, has not yet been performed in human hypertrophic scars (HS). The present study compared the expression levels of lncRNAs, circRNAs and mRNAs in human HS and normal skin tissues by high-throughput RNA sequencing. Numerous differentially expressed lncRNAs, circRNAs and mRNAs were detected. Subsequently, five aberrantly expressed lncRNAs and mRNAs, and six circRNAs were measured to verify the RNA sequencing results by reverse transcription-quantitative polymerase chain reaction. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed for the dysregulated genes, in order to elucidate their principal functions. In addition, a coding-noncoding gene co-expression (CNC) network and ceRNA network were constructed for specific significantly altered genes. The CNC network analysis suggested that AC048380.1 and LINC00299 were associated with metastasis-related genes, including inhibin subunit βA (INHBA), SMAD family member 7 (SMAD7), collagen type I α1 chain (COL1A1), transforming growth factor β3 (TGFβ3) and MYC proto-oncogene, bHLH transcription factor (MYC). Inhibitor of DNA binding 2 was associated with the lncRNAs cancer susceptibility 11, TGFβ3-antisense RNA 1 (AS1), INHBA-AS1, AC048380.1, LINC00299 and LINC01969. Circ-Chr17:50187014_50195976_-, circ-Chr17:50189167_50194626_-, circ-Chr17:50189167_ 50198002_- and circ-Chr17:50189858_50195330_- were also associated with INHBA, SMAD7, COL1A1, TGFβ3 and MYC. COL1A1 and TGFβ3 were associated with circ-Chr9:125337017_125337591_+ and circ-Chr12:120782654_120784593_-. The ceRNA network indicated that INHBA-AS1 and circ-Chr9:125337017_125337591_+ were ceRNAs of microRNA-182-5p targeting potassium voltage-gated channel subfamily J member 6, ADAM metallopeptidase with thrombospondin type 1 motif 18, SRY-box 11, MAGE family member L2, matrix metallopeptidase 16, thrombospondin 2, phosphodiesterase 11A and collagen type V a1 chain. These findings suggested that lncRNAs and circRNAs may act as ceRNAs, which are implicated in the pathophysiology and development of human HS, and lay a foundation for further insight into the novel regulatory mechanism of lncRNAs and circRNAs in hypertrophic scarring.

"Genetic regulation of Mycobacterium tuberculosis in a lipid-rich environment"

Tuberculosis (TB) remains as one of the leading causes of morbidity and mortality among infectious diseases worldwide. Although lipids (mainly fatty acids and cholesterol) have been reported to play an important role during active and latent infection of M. tuberculosis, there are other molecular aspects of bacterial response to those substrates that are not fully understood, involving gene regulation background. This review highlights recent insights on pathogen gene expression: regulation during its active growth, during survival in presence of lipids and under variable hostile host microenvironments. We also propose several application options of this knowledge that may contribute for improved TB control.

The Mycobacterium tuberculosis transcriptional landscape under genotoxic stress

Background

As an intracellular human pathogen, Mycobacterium tuberculosis (Mtb) is facing multiple stressful stimuli inside the macrophage and the granuloma. Understanding Mtb responses to stress is essential to identify new virulence factors and pathways that play a role in the survival of the tubercle bacillus. The main goal of this study was to map the regulatory networks of differentially expressed (DE) transcripts in Mtb upon various forms of genotoxic stress. We exposed Mtb cells to oxidative (H₂O₂ or paraquat), nitrosative (DETA/NO), or alkylation (MNNG) stress or mitomycin C, inducing double-strand breaks in the DNA. Total RNA was isolated from treated and untreated cells and subjected to high-throughput deep sequencing. The data generated was analysed to identify DE genes encoding mRNAs, non-coding RNAs (ncRNAs), and the genes potentially targeted by ncRNAs.

Results

The most significant transcriptomic alteration with more than 700 DE genes was seen under nitrosative stress. In addition to genes that belong to the replication, recombination and repair (3R) group, mainly found under mitomycin C stress, we identified DE genes important for bacterial virulence and survival, such as genes of the type VII secretion system (T7SS) and the proline-glutamic acid/proline-proline-glutamic acid (PE/PPE) family. By predicting the structures of hypothetical proteins (HPs) encoded by DE genes, we found that some of these HPs might be involved in mycobacterial genome maintenance. We also applied a state-of-the-art method to predict potential target genes of the identified ncRNAs and found that some of these could regulate several genes that might be directly involved in the response to genotoxic stress.

Conclusions

Our study reflects the complexity of the response of Mtb in handling genotoxic stress. In addition to genes involved in genome maintenance, other potential key players, such as the members of the T7SS and PE/PPE gene family, were identified. This plethora of responses is detected not only at the level of DE genes encoding mRNAs but also at the level of ncRNAs and their potential targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3132-1) contains supplementary material, which is available to authorized users.

RNA-Seq analysis uncovers non-coding small RNA system of Mycobacterium neoaurum in the metabolism of sterols to accumulate steroid intermediates

BACKGROUND

Understanding the metabolic mechanism of sterols to produce valuable steroid intermediates in mycobacterium by a noncoding small RNA (sRNA) view is still limited. In the work, RNA-seq was implemented to investigate the noncoding transcriptome of Mycobacterium neoaurum (Mn) in the transformation process of sterols to valuable steroid intermediates, including 9α-hydroxy-4-androstene-3,17-dione (9OHAD), 1,4-androstadiene-3,17-dione (ADD), and 22-hydroxy-23, 24-bisnorchola-1,4-dien-3-one (1,4-BNA).

RESULTS

A total of 263 sRNA candidates were predicted from the intergenic regions in Mn. Differential expression of sRNA candidates was explored in the wide type Mn with vs without sterol addition, and the steroid intermediate producing Mn strains vs wide type Mn with sterol addition, respectively. Generally, sRNA candidates were differentially expressed in various strains, but there were still some shared candidates with outstandingly upregulated or downregulated expression in these steroid producing strains. Accordingly, four regulatory networks were constructed to reveal the direct and/or indirect interactions between sRNA candidates and their target genes in four groups, including wide type Mn with vs without sterol addition, 9OHAD, ADD, and BNA producing strains vs wide type Mn with sterol addition, respectively. Based on these constructed networks, several highly focused sRNA candidates were discovered to be prevalent in the networks, which showed comprehensive regulatory roles in various cellular processes, including lipid transport and metabolism, amino acid transport and metabolism, signal transduction, cell envelope biosynthesis and ATP synthesis. To explore the functional role of sRNA candidates in Mn cells, we manipulated the overexpression of candidates 131 and 138 in strain Mn-9OHAD, which led to enhanced production of 9OHAD from 1.5- to 2.3-fold during 6 d' fermentation and a slight effect on growth rate.

CONCLUSIONS

This study revealed the complex and important regulatory roles of noncoding small RNAs in the metabolism of sterols to produce steroid intermediates in Mn, further analysis of which will promote the better understanding about the molecular metabolism of these sRNA candidates and open a broad range of opportunities in the field.