Abstract
MicroRNAs (miRNA) are small non-coding RNAs that negatively regulate gene expression in a sequence- specific manner. Post-transcriptional silencing of target genes by miRNA occurs either by specific cleavage of homologous mRNA or by specific inhibition of protein synthesis. MiRNAs are essential regulators of various processes such as proliferation, differentiation, development, cell death and interaction between virus and host cell. The aim of this paper is to summarize the main findings from research on miRNA biogenesis, functionality and cancer relevance. A narrative literature review of all of the relevant papers known to the authors was conducted. Several human diseases including cancer are associated with aberrant regulation of miRNAs expression or deficiency in miRNA biogenesis. Analysis of miRNA expression signatures can serve as a valuable tool for cancer classification, diagnostics and prediction of tumor behavior. There has been demonstrated a possibility to use these microRNA signatures for a specific cancer classification with potential predictive and therapeutic value. The known data provide evidence that microRNAs may open new ways for cancer diagnosis, prognosis estimation and therapy.
Highlights
Recent discovery of several types of non-protein-coding RNAs, such as small nucleolar RNAs, small interfering RNAs, microRNAs and antisense RNAs indicate that the transcriptomes of higher eukaryotes are much more complex than originally anticipated
Inactivation of genes related to RNA interference (RNAi) pathway causes heterochronic phenotypes similar to lin-4 and let-7 mutations[34]. These findings suggest that miRNas have an essential role in C. elegans embryogenesis and larval development
Chen et al (2004) described a virulence factor encoded by turnip yellow mosaic virus, p69, which suppresses the antiviral small interfering RNAs (siRNAs) pathway but promotes the miRNA pathway in Arabidopsis thaliana. p69 suppression of the siRNA pathway is upstream of double-stranded RNA (dsRNA) and is as effective as genetic mutations in A. thaliana genes involved in dsRNA production. p69-expressing plants exhibited disease-like symptoms in the absence of viral infection, these findings suggest a novel mechanism for viral virulence by promoting the miRNA-guided inhibition of host gene expression[56]
Summary
Recent discovery of several types of non-protein-coding RNAs, such as small nucleolar RNAs, small interfering RNAs, microRNAs and antisense RNAs indicate that the transcriptomes of higher eukaryotes are much more complex than originally anticipated. These RNAs serve as modulators of gene expression in a sequence specific manner. MicroRNAs (miRNA) are small RNA molecules encoded in genomes of plants, animals, fungi and viruses. These highly conserved RNAs regulate gene expression by specific inhibition of translation, induction of mRNA cleavage and DNA methylation. MiRNAs are essential regulators of various processes such as proliferation, differentiation, development, cell death and interaction between virus and host cell
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