MicroRNAs (miRNAs) are a broad class of non-coding RNA that is approximately 21 nucleotides in length and play crucial roles in post-transcriptional gene regulation procedures. These molecules involved in many developmental and cellular processes in eukaryotic organisms.
Current investigation has reported major factors contributing to miRNA biogenesis and has constituted basic principles of miRNA function. More recently, it was established that different miRNAs are clearly concerned in human malignancies, such as lung, breast, ovarian, bladder, colon and squamous-cell carcinoma. In addition, dysregulations in the miRNA machinery components such as Dicer, Drosha, DGCR8, Argonaut, and TRBP could be involved in carcinogenesis of many cancers. The purpose of the current review was to summarize growing comprehension besides how miRNA biogenesis and gene silencing are changed to promote cancer.
Key Words: DGCR8, miRNA machinery components, miR, Cancers, Regulator IntroductionSeveral Classes of small non-coding RNAs including, small interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs) and microRNAs (miRNAs) have a principal and crucial regulatory roles of development procedures in all eukaryotes (1). Formerly, a finding revealed that of the first miRNAs in Caenorhabditis elegans organism (2). miRNAs are extremely protected among species, and more significantly, it has been predictable that miRNAs may regulate up to 30% of all genes in the human genome (3, 4). miRNAs are small non coding RNAs of 18–24 nucleotides (nt) in length that control gene expression post-transcriptional (5), that negatively regulate through binding to the 3′ untranslated region (3′ UTR) of messenger RNA (mRNA) transcripts, stimulation translational suppression or cleavage of the target (6, 7). Several thousands of miRNAs have been identified in humans and they are evolutionarily conserved.
Recently, it has been uncovered that variable expression of special miRNA genes could be increased to the initiation and progression of diseases such as cancers (8). Accordingly, cancer-associated altered in miRNA expression patterns are emerging as promising diagnostic markers that often associate with disease progression and survival rates. This pathway, maybe also demonstrated as a new window for treatment of different types of cancers (9). In general, miRNAs can be controlled several procedures, including metabolism, survival cells, inflammation, genome stability, cell differentiation and proliferation, invasion and angiogenesis to affect malignant development (10). Appearing in the cell nucleus, miRNA operation continues in the regulation of gene expression by coupled with its supplementary base-sequence of the targeted mRNA molecule in the cytoplasm.
Subsequently, gene silencing through degradation of target mRNA or interference in the translation process taken place (11). These discoveries led to the development of more and sufficient for research in this area such that now hundreds of microRNAs have been identified in different species (12). However, most miRNA research centralized on the growth and development of stem cells, differentiation, tumorigenesis and other pathological processes (13).