MicroRNAs (miRNAs) are short, 20-22 nucleotide RNA molecules that function as negative regulators of gene expression in eukaryotic organisms. RNA mediated gene silencing pathways have essential roles in development, cell differentiation, proliferation, and cell death. It is becoming clear that microRNAs can play a very important role in regulation of gene expression. Understanding the basic mechanism of miRNA biogenesis is one of the central aims of molecular biologists in the future. MicroRNA molecules are produced from hairpin precursors formed from large transcripts. Two RNase III endonucleases, Drosha and Dicer, cleave both strands of the RNA and generate 20-22 nucleotide miRNA duplex. One arm of the duplex is selected and incorporated into RNA-induced silencing complex (RISC). RISC was identified earlier to repress the translation of mRNA in the presence of small interfering RNAs (siRNAs) by RNA interference (RNAi) mechanism. In animal cells, single-stranded miRNAs associated with RISC usually bind to target mRNAs through partial base-pairing, and result in translational repression. In plants, most miRNAs trigger mRNA cleavage through perfect base-pairing between miRNAs and target mRNAs. MiRNAs play important roles in development and diseases of plants and animals. There might be a possibility to use these microRNA signatures for a specific cancer classification with potential predictive and therapeutic value. MicroRNAs are aberrantly expressed in all studied cancer tissues. They are often located in cancer-associated genomic regions, act as tumor suppressors or oncogenes. For instance, miR-17–92, miR-155, miR-21, which are over expressed in tumors, might be considered as oncogenes. MiRNAs, such as let-7, which expression is reduced in cancer cells, can act as tumor-suppressor. 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 relevant papers known to the authors was conducted.
|Uddannelser||Molekylærbiologi, (Bachelor/kandidatuddannelse) Bachelor el. kandidat|
|Udgivelsesdato||28 jun. 2007|
|Vejledere||Louise Torp Dalgaard|