NcRNAs are classified into (i) housekeeping, for the maintenance of normal cell functionalities (such as ribosomal (rRNA) or transfer (tRNA)); and (ii) regulatory ncRNAs. Regulatory ncRNAs include short (small) ncRNAs (<200 nucleotides, sncRNAs) and long ncRNAs (>200 nucleotides, lncRNAs). The sncRNAs (siNRA, miRNA, piRNA) are extensively studied in the last decade and have been associated with RNA interference (RNAi) pathways, which lead to silencing of specific genes and protection of the cell or genome against foreign nucleic acids[i]. For example, ncRNAs are indispensable in tumorigenesis by regulating the expression of tumor-related genes[ii]. Involvement of ncRNAs in disease processes by deregulation in the expression patterns of these ncRNA is illustrated in the figure [iii].
[i] Moazed D Review Small RNAs in transcriptional gene silencing and genome defence. Nature. 2009 Jan 22; 457(7228):413-20.
[ii] Liu, L., Wang, Q., Qiu, Z. et al. Noncoding RNAs: the shot callers in tumor immune escape. Sig Transduct Target Ther 5, 102 (2020). https://doi.org/10.1038/s41392-020-0194-y
[iii] Gomes AQ, Nolasco S, Soares H. Non-coding RNAs: multi-tasking molecules in the cell. Int J Mol Sci. 2013 Jul 31;14(8):16010-39. doi: 10.3390/ijms140816010. PMID: 23912238; PMCID: PMC3759897.