A non-coding RNA (ncRNA) is a functional RNA molecule that is transcribed from DNA but never translated into protein, acting instead as RNA in its own right; the unifying theme across its classes is that most participate in transcription or translation, either as machinery or as regulators. The principal classes are microRNA (miRNA), which regulates gene expression transcriptionally and post-transcriptionally by base-pairing with complementary sequences in messenger RNA to cause translational repression or target degradation; ribosomal RNA (rRNA), the RNA component of the ribosome; transfer RNA (tRNA), the adaptor linking mRNA codons to their corresponding amino acids; small nucleolar RNA (snoRNA), which guides covalent modification of other RNAs by methylation and pseudouridylation; and small nuclear RNA (snRNA), which processes pre-mRNA in the nucleus and, complexed with proteins as small nuclear ribonucleoproteins (snRNPs), forms the spliceosome that excises introns and ligates exons. The concept belongs to molecular biology and RNA biology, extending the central dogma by establishing that protein is not the only functional endpoint of gene expression.
A non-coding RNA (ncRNA) is a functional RNA molecule that is transcribed from DNA but never translated into protein, acting instead as RNA in its own right; the unifying theme across its classes is …