The Role of microRNAs in the viral Infections.

MicroRNAs (miRNAs) are non-coding RNAs with 19 to 24 nucleotides which are evolutionally conserved. MicroRNAs play a regulatory role in many cellular functions such as immune mechanisms, apoptosis, and tumorigenesis. The main function of miRNAs is the post-transcriptional regulation of gene expression via mRNA degradation or inhibition of translation. In fact, many of them act as an oncogene or tumor suppressor. These molecular structures participate in many physiological and pathological processes of the cell. The virus can also produce them for developing its pathogenic processes. It was initially thought that viruses without nuclear replication cycle such as Poxviridae and RNA viruses can not code miRNA, but recently, it has been proven that RNA viruses can also produce miRNA. The aim of this articles is to describe viral miRNAs biogenesis and their effects on cellular and viral genes.