sncRNA-1 Is a Small Noncoding RNA Produced by Mycobacterium tuberculosis in Infected Cells That Positively Regulates Genes Coupled to Oleic Acid Biosynthesis

A review of the human microRNA and the Mycobacterium tuberculosis epigenetic effects on the emergence drug resistance

AIMS

Mycobacterium tuberculosis (MTB) uses epigenetics to avoid the hostile host immune defence systems and also mount resistance to chemotherapy when exposed to antibiotic stress. MTB's epigenetic survival tool-kit includes genomic DNA histone acetylation/deacetylation, methylation, phosphorylation, ubiquitylation, etc. The non-coding host microRNAs (miRNAs) as genomic products of epigenetic control of drug extrusion processes, drug permeability barrier formation or metabolism, and target alteration are hijacked by MTB to mount multi-drug resistance. The miRNAs involved and the mechanisms used are not yet completely understood. The role of MTB genome-derived miRNA are currently indeterminate as the current studies are only focused on the host miRNA biogenesis in MTB pathogenesis. However, the contribution of host miRNA to drug resistance in MTB chemotherapy is largely unknown..

MATERIALS AND METHODS

We have comprehensively searched online databases for medical, health, and nanotechnology for articles published in English between 2020 and 2024 using search words "MTB", "Epigenetics", "microRNA", "TB Chemotherapy" to compile this narrative review.

KEY FINDINGS

MTB epigenetic tool-kit of DNA methylation, histone acetylation/deacetylation, cell membrane impermeability, drug metabolism and target mimicry are mediated by the hijacked host cell microRNAs in the development of drug resistance. Antisense oligomers or mimetics can therefore, be used as miRNA antagonists/silencers or agomirs, respectively, depending on the pattern of miRNA expression, to combat resistance to MTB chemotherapy.

CONCLUSIONS

This review discusses microRNAs as epigenetic agents in the emergence of Multi-Drug Resistance TB (MDR-TB) and their potential role in chemotherapeutics.

Mycobacterium tuberculosis complex molecular networks and their regulation: Implications of strain heterogeneity on epigenetic diversity and transcriptome regulation

Tuberculosis has been a public health crisis since the 1900, which has caused the highest mortalities due to a single bacterial infection worldwide, that was recently further complicated by the Coronavirus disease 2019 pandemic. The causative agent of Tuberculosis, Mycobacterium tuberculosis, belongs to a genetically well-characterized family of strains known as the Mycobacterium tuberculosis complex, which has complicated progress made towards eradicating Tuberculosis due to pathogen-specific phenotypic differences in the members of this complex. Mycobacterium tuberculosis complex strains are genetically diverse human- and animal-adapted pathogens belonging to 7 lineages (Indo-Oceanic, East-Asian, East-African Indian, Euro-American, M. africanum West Africa 1, M. africanum West Africa 2 and Ethopia), respectively and the recently identified Lineage 8 and M. africanum Lineage 9. Genomic studies have revealed that Mycobacterium tuberculosis complex members are ∼99 % similar, however, due to selective pressure and adaptation to human host, they are prone to mutations that have resulted in development of drug resistance and phenotypic heterogeneity that impact strain virulence. Furthermore, members of the Mycobacterium tuberculosis complex have preferred geographic locations and possess unique phenotypic characteristics that is linked to their pathogenicity. Due to the recent advances in development next generation sequencing platforms, several studies have revealed epigenetic changes in genomic regions combined with "unique" gene regulatory mechanisms through non-coding RNAs that are responsible for strain-specific behaviour on in vitro and in vivo infection models. The current review provides up to date epigenetic patterns, gene regulation through non-coding RNAs, together with implications of these mechanisms in down-stream proteome and metabolome, which may be responsible for "unique" responses to infection by members of the Mycobacterium tuberculosis complex. Understanding lineage-specific molecular mechanisms during infection may provide novel drug targets and disease control measures towards World Health organization END-TB strategy.

Small RNAs Asserting Big Roles in Mycobacteria

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb), with 10.4 million new cases per year reported in the human population. Recent studies on the Mtb transcriptome have revealed the abundance of noncoding RNAs expressed at various phases of mycobacteria growth, in culture, in infected mammalian cells, and in patients. Among these noncoding RNAs are both small RNAs (sRNAs) between 50 and 350 nts in length and smaller RNAs (sncRNA) < 50 nts. In this review, we provide an up-to-date synopsis of the identification, designation, and function of these Mtb-encoded sRNAs and sncRNAs. The methodological advances including RNA sequencing strategies, small RNA antagonists, and locked nucleic acid sequence-specific RNA probes advancing the studies on these small RNA are described. Initial insights into the regulation of the small RNA expression and putative processing enzymes required for their synthesis and function are discussed. There are many open questions remaining about the biological and pathogenic roles of these small non-coding RNAs, and potential research directions needed to define the role of these mycobacterial noncoding RNAs are summarized.

Cobalamin is present in cells of non-tuberculous mycobacteria, but not in Mycobacterium tuberculosis

Cobalamin (vitamin B12) is a structurally complex molecule that acts as a cofactor for enzymes and regulates gene expression through so-called riboswitches. The existing literature on the vitamin B12 synthesis capacity in Mycobacterium tuberculosis is ambiguous, while in non-tuberculous mycobacteria (NTM) is rather marginal. Here we present the results of our investigation into the occurrence of vitamin B12 in mycobacteria. For detection purposes, immunoassay methods were applied to cell lysates of NTM and M. tuberculosis clinical and laboratory strains grown under different conditions. We show that whereas vitamin B12 is present in cells of various NTM species, it cannot be evidenced in strains of differently cultured M. tuberculosis, even though the genes responsible for vitamin B12 synthesis are actively expressed based on RNA-Seq data. In summary, we conclude that the production of vitamin B12 does occur in mycobacteria, with the likely exception of M. tuberculosis. Our results provide direct evidence of vitamin B12 synthesis in a clinically important group of bacteria.