Noncoding RNAs as critical players in regulatory accuracy, redox signaling, and immune cell functions

The transcriptome of multicellular organisms is much more complex than initially thought because it includes a large number of noncoding RNAs (ncRNAs). Data regarding ncRNAs suggest that organism complexity better correlates with the percentage of each genome that is transcribed into these molecules. The most studied classes of ncRNAs are short interfering RNAs, microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), and long noncoding RNAs (lncRNAs). In this chapter, we review the biogenesis pathways and general functions of miRNAs, piRNAs, and lncRNAs. We focus on the roles of miRNAs and lncRNAs in gene expression regulation, centering on redox signaling and immune cell development, and highlight some implications for human pathologies. Finally, we analyze current knowledge concerning the use of ncRNAs in diagnosis, prognosis, and therapeutics, and discuss their role in the development of the immune system and the regulatory functions of H2O2 during the course of metazoan evolution.