| RNA species | Length (nt) | Number* | Origin | RNAP | Role / Comments | Reference / Comments |
|---|---|---|---|---|---|---|
| Translation | ||||||
| mRNA - messenger | < 1K to > 100K | > 25K | Genome / hnRNA (pre-mRNA) | Pol II | Translation, encodes protein sequences | |
| rRNA - ribosomal | 5S:121, 5.8S:156, 28S:5070; 18S:1869 | ~200 | Genome | Pol I 45S / Pol III 5S | Translation, ribosome structure, peptidyl transferase; lengths are for Human / Eukaryotic ribosomes | |
| tRNA - transfer | 70 to 100 | > 600 | Genome | Pol III | Translation, brings amino acids to the ribosome | |
| snRNA - small nuclear | ~150 | 1674 | Genome | Splicing | https://en.wikipedia.org/wiki/Small_nuclear_RNA https://rnajournal.cshlp.org/content/27/10/1186.full | |
Sm-class snRNA | Pol II (most) | Splicing - U1, U2, U4, U4atac, U5, U7, U11, and U12 - assembled in the cytoplasm and return to the nucleus; named U for high in uridine | https://en.wikipedia.org/wiki/Small_nuclear_RNA | |||
Lsm-class snRNA | Pol III | Splicing U6, U6atac - never leave the nucleus | https://en.wikipedia.org/wiki/Small_nuclear_RNA | |||
| snoRNA - small nucleolar | 50 to 250 | 475 | Genome, introns | Pol II | RNA modification, guide rRNA, tRNA, snRNA, can function as miRNA | https://en.wikipedia.org/wiki/Small_nucleolar_RNA https://bioinfo-scottgroup.med.usherbrooke.ca/snoDB/statistics/ https://genomebiology.biomedcentral.com/articles/10.1186/s13059-021-023… |
scaRNA - cajal | 50 to 251 | Genome | Pol II (most), Pol III | RNA modification - guide methylation and pseudouridylation in Cajal bodies in actively growing cells | https://en.wikipedia.org/wiki/Cajal_body | |
| Regulation | ||||||
| tsRNA - tRNA derived small | interact with proteins / mRNA, inhibit translation, regulate gene expression / cell cycle / chromatin / epigenetic modifications. | |||||
tiRNA - tRNA halves | 35 to 50 | > 1200 | tRNA - Angiogenin (ANG) | ANG is ribonuclease 5 which also stimulates new blood cells; numbers estimated from tRNAs | https://www.nature.com/articles/s41392-020-00217-4 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3160621 | |
tRF - tRNA fragments | < 35 | > 1200 | tRNA - Dicer, ANG, others | Block peptidyl transferase, can overlap with miRNA; numbers estimated from tRNAs | https://www.nature.com/articles/s41392-020-00217-5 | |
| circRNA - circular | < 100 to > 4K | 90K | hnRNA, introns | Regulate miRNA by acting as molecular sponges | https://en.wikipedia.org/wiki/Circular_RNA https://molecular-cancer.biomedcentral.com/articles/10.1186/s12943-017-… https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4238349/ | |
| lncRNA - long non-coding | > 200 | 30K-60K | Genome, hnRNA | Pol II, Pol III | Regulate transcription via multiple mechanisms, have tissue specificity | https://en.wikipedia.org/wiki/Long_non-coding_RNA https://www.nature.com/articles/s41467-019-13688-z |
XistRNA | 17K | 1 | Genome | Pol II | X-chromosome inactivation - capped, poly A | https://en.wikipedia.org/wiki/Long_non-coding_RNA |
HOTAIR - HOX antisense intergenic | 2158 | 1 | Genome | Pol II | Cancer progression - capped, poly A | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383848/ |
| Anti-Sense RNA | 19-23 | > 5000 | Genome | Pol II | Blocks translation by hybridizing with mRNA can be miRNA, lncRNA, or synthetic DNA / RNA (antisense oligonucleotides/oligodeoxynucleotides [ASOs]) | https://en.wikipedia.org/wiki/Antisense_RNA https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6194357/F23 https://academic.oup.com/nar/article/32/16/4812/1023283 |
cis | 19 to 24 | Genome - sense strand | Pol II | Generally specific for mRNA they are associated with - high complementarity | https://en.wikipedia.org/wiki/Antisense_RNA | |
trans | 19 to 25 | Genome - elsewhere | Pol II | Can target multiple mRNAs - low complementarity | https://en.wikipedia.org/wiki/Antisense_RNA | |
| Y RNA - not U | 100 | 4 / 5 | Genome | Pol III | Y1, Y3, Y4 and Y5 (Y2 is a truncated form of Y1), DNA replication, RNA stability, stress responses | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7363058/ https://www.frontiersin.org/articles/10.3389/fimmu.2018.03164/full |
| RNAi - RNA Interference | Genome | https://en.wikipedia.org/wiki/RNA_interference | ||||
miRNA - micro | 21 to 23 | > 2300 | Genome | Pol II | RNA silencing and post translational regulation - bind complementary sites in mRNA via RNA-induced silencing complex (RISC); processed by Dicer, Argonaute | https://en.wikipedia.org/wiki/MicroRNA |
stRNA - small temporal | 21 to 25 | Genome | Pol II | Development role in C. elegans (worm) | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3419770/ | |
siRNA - small interfering | 20 to 24 | Genome, exogenic | Pol II, Pol IV (plants) | mRNA cleavage at siRNA binding sites via RISC; processed by Dicer, Argonaute | https://www.frontiersin.org/articles/10.3389/fpls.2020.526455/full | |
piRNA - PIWI inteacting | 26 to 31 | ~20K | Genome | Pol II | Several rolls, can circulate in stable forms, RNA silencing, transposon defense; PIWI is a subfamily of Argonaute | https://www.frontiersin.org/articles/10.3389/fmolb.2022.848105/full https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6392428/ |
rasiRNA - repeat associated | 24 to 27 | Genome | Pol II, Pol IV (plants) | Chromatin silencing; not described in mammals; processed by Dicer, Argonaute | https://www.frontiersin.org/articles/10.3389/fimmu.2018.03164/full | |
| exRNA - exogenous | all | > 100K | ncRNA, some mRNA | Packaged in lipids, vesicles, proteins; can serve as biomarkers and intercellular regulation | https://en.wikipedia.org/wiki/Extracellular_RNA | |
Notes:
- Each RNA species name includes the terms indicated by its prefix.
- Except were noted data are for human.
- Numbers of RNA species were obtain from Google searches of "how many xRNA are in the human genome" and returned references.
- References are links to wikipedia and articles in PubMed or journal sites.