Non-coding RNAs and gene silencing

RNA interference (RNAi) is a mechanism that regulates gene expression. It is formed of several different pathways that facilitate gene silencing and negative regulation of expression through non-coding small RNA particles like small interfering RNA (siRNA) and microRNA (miRNA). These noncoding RNA particles participate in the regulation of important biological processes like development, proliferation, differentiation and apoptosis. Although siRNAs can have either exogenous or endogenous origin, miRNAs are derived from endogenous sources and miRNAs do not display the absolute specificity of binding to their target mRNAs like siRNAs. In recent years, it has been shown that abnormalities in miRNA function have an important role in the etiopathology of many diseases like cancer. The evaluation of miRNA expression in cancerous tissues provides information on the prognosis of cancer and thus enable miRNAs to be used as tumor markers. Since miRNAs, like transcriptions factors, act in different combinations in the regulation of several genes, it does not seem possible to use them in therapeutical context. Hence, application of siRNAs which bind their targets with higher specificity, by different delivery methods makes them more promising therapeutical agents for the treatment of cancer, human immunodeficiency virus infection, and neurological disorders in the future.