Table 1.
Different types of non-coding RNAs involved in human cancers (modified after Sana et al.[107]).
| Type | Class | Symbol | Characteristic | Cancer/biological function associations |
|---|---|---|---|---|
| Long non-coding RNAs (lncRNAs, ≥200 nt) | Long intergenic non-coding RNAs | lincRNAs | ranging from several hundreds to tens of thousands nts; lie within the genomic intervals between two genes; transcriptional | involved in tumorigenesis and cancer metastasis/involved in diverse biological processes such as dosage compensation and/or imprinting |
| Long intronic non-coding RNAs | cis-regulation of neighbouring genes lie within introns; evolutionary conserved; tissue-specific expression patterns | aberrantly expressed in human cancers/possible link with posttranscriptional gene silencing | ||
| Telomere-associated ncRNAs | TERRAs | 100 bp >9 kb; conserved among eukaryotes; synthesized from C-rich strand; polyadenylated; form intermolecular G-quadruplex structure with single-stranded telomeric DNA | possible impact on telomere-associated diseases including many cancers/negative regulation of telomere length and activity through inhibition of telomerase | |
| Long non-coding RNAs with dual functions | both protein-coding and functionally regulatory RNA capacity | deregulation has been described in breast and ovarian tumors/modulate gene expression through diverse mechanisms | ||
| Pseudogene RNAs | gene copies that have lost the ability to code for a protein; potential to regulate their protein-coding cousin; created via retrotrans-positions; tissue-specific | often deregulated during tumorigenesis and cancer progression/regulation of tumor suppressors and oncogenes by acting as microRNA decoys | ||
| Transcribed-ultraconserved regions | T-UCRs | longer than 200 bp; absolutely conserved between orthologous regions of human, rat, and mouse; located in both intra- and intergenic regions | expression is often altered in some cancers; possible involvement in tumorigenesis; antisense inhibitors for protein-coding genes or other ncRNAs | |
| Antisense RNAs | aRNAs | complementary antisense transcripts | antisense transcripts appear to be a pervasive feature of human cells, which suggests that they are a fundamental component of gene regulation | |
| Long stress-induced non-coding transcripts | LSINCTs | longer than 300 nucleotides; expression is increased in response to the DNA damage-inducing tobacco carcinogen 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone (NNK) | increased expression in a number of cancer-derived cell lines | |
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| Small non-coding RNAs (<200 nt) | MicroRNAs | miRNAs | 18–25 nt; account 1%–2% of the human genome; control the 50% of protein-coding genes; guide suppression of translation; Drosha- and Dicer-dependent small ncRNAs | initiation of various disorders including many, if not all, cancers/regulation of proliferation, differentiation, and apoptosis; involved in human development |
| Small nucleolar RNAs | snoRNAs | 60–300 nt; enriched in the nucleolus; excised from pre-mRNA introns in vertebrates; bind snoRNP proteins | association with development of some cancers/important function in the maturation of other non-coding RNAs, above all, rRNAs and snRNAs; miRNA-like snoRNAs regulate mRNAs | |
| Pyknons | subset of patterns of variable length; form mosaics in untranslated and protein-coding regions; more frequently in 3′ UTRs | expected association with cancer biology/possible link with posttranscriptional silencing of genes, mainly involved in cell communication, regulation of transcription, signaling, transport, etc. | ||