ncRNAs: types, average nucleotide (nt) lengths, and key functions
| Class | Type | Length (nt) | Function | |
|---|---|---|---|---|
| Housekeeping ncRNAs | Ribosomal RNA (rRNA) | > 1,500 | Protein synthesis | |
| Transfer RNA (tRNA) | 76–90 | Protein synthesis | ||
| Small nuclear RNA (snRNA) | 100–300 | RNA processing | ||
| Small nucleolar RNA (snoRNA) | 60–200 | Pre-mRNA processing | ||
| Regulatory ncRNAs | Short ncRNAs (< 200 nt) | MicroRNA (miRNA) | 18–22 | Protein translation regulation |
| Small interfering RNA (siRNA) | 20–25 | Post-translation mRNA regulation; antiviral defense | ||
| Piwi-interacting RNA (piRNA) | 26–31 | Silencing of transposable elements | ||
| Long ncRNAs (> 200 nt) | Long ncRNAs (lncRNAs) | ~ 1 kb | Spatiotemporal gene expression (cell differentiation); modification of 3D chromatin architecture; protein scaffolding; miRNA sponging | |
| Circular RNA (circRNA) | 100–999 | miRNA sponging; protein scaffolding; gene expression (cell/tissue development) | ||
3D: three-dimensional; ncRNAs: noncoding RNAs