Читать книгу Algorithms in Bioinformatics - Paul A. Gagniuc - Страница 24

RNAs have multiple and versatile roles across all biological systems and one of the roles is mRNA silencing and post-transcriptional regulation of gene expression. Small RNAs are short (∼18–30 nucleotides), noncoding RNA molecules that can regulate gene expression in both the cytoplasm and the nucleus. A few classes of small RNAs have been defined, such as microRNAs (miRNAs), small interfering RNAs (siRNAs), and Piwi-interacting RNAs (piRNAs) [63]. For instance, miRNAs are small noncoding RNA molecules (∼21–25 nucleotides in length) that play an important regulatory role in animals and plants by targeting specific mRNAs for degradation or translation repression [64, 65]. It appears that an imperfect complementary between miRNAs and different mRNA targets has the potential to regulate several genes simultaneously. Moreover, miRNAs cross the boundary of a single cell. To add to the complexity of these processes, some miRNAs are secreted into exosomes or microvesicles and may have the ability to move through circulation to other distant cells or tissues [66–68]. Without question, the fine-grained regulation that underlies the complexity of eukaryotes is found in these short RNA molecules.