Table 2.
Types of human noncoding RNAs.
| Types | Subclasses | Symbol | Biological functions | Illustrative examples | References |
|---|---|---|---|---|---|
| Small noncoding RNAs (~20–200 nt) | PIWI-interacting RNAs | piRNAs | Repression of mobile elements and other genetic elements in germ line cells | LINE1 piRNAs; piR-823 | [74, 75] |
| Small interfering RNAs | siRNAs | Gene silencing and defense against pathogen nucleic acids | Oocyte endo-siRNAs; L1-specific siRNA | [76, 77] | |
| microRNAs | miRNAs | Posttranscriptional regulation of gene expression | lin-4; miR-139 | [78, 93] | |
|
| |||||
| Long noncoding RNAs (200 nt to ~100 kb) | Intergenic noncoding RNAs | lincRNAs | Regulation of chromatin remodeling and imprinting | HOTAIR; XIST | [108] |
| Transcribed ultraconserved regions | T-UCRs | Regulation of genes miRNAs and methylation | uc.160; uc.283A | [109] | |
| Circular RNAs | circRNAs | Modulation of miRNA and RNA-binding proteins | CDR1as; SRY | [110] | |