MicroRNA, RNA interference and antisense drugs
Short RNAs can switch off a gene after it has been copied into mRNA; cells use them naturally, and medicine now uses them as drugs.
Key facts
- MicroRNAs (miRNAs) are made by the cell and are about 22 nucleotides long; each pairs partly with many mRNAs and lowers their translation or stability.
- Small interfering RNAs (siRNAs) pair exactly with one mRNA; loaded into the RISC complex, they guide it to cut that mRNA.
- Antisense oligonucleotides are short, chemically modified single strands that bind a target RNA and cause its breakdown or change its splicing.
- These drugs lower or correct a protein without changing the DNA.
In detail
- miRNA genes are transcribed, trimmed by Drosha in the nucleus and by Dicer in the cytoplasm, and then work inside RISC.
- One miRNA can tune hundreds of genes; miRNA levels are altered in many cancers.
- Getting the drug to its tissue is the main problem: liver-targeted siRNAs are often linked to GalNAc, a sugar that liver cells take up.
- Splice-switching antisense drugs can make the cell skip an exon (some Duchenne treatments) or keep one (nusinersen in spinal muscular atrophy).
- Also called
- miRNA and siRNA, RNA silencing
Clinical notes
- Inclisiran, an siRNA against PCSK9, lowers LDL cholesterol.
- siRNA and antisense drugs that lower transthyretin are used in hereditary transthyretin amyloidosis.
- Lumasiran, an siRNA, reduces oxalate production in primary hyperoxaluria type 1.
- Nusinersen changes SMN2 splicing so that more working SMN protein is made.
Test yourself
Think of the answer, then tap the question to see it.
How does an siRNA differ from a microRNA?
An siRNA pairs exactly with one mRNA and leads to its cleavage; a microRNA pairs partly with many mRNAs and mainly dampens their translation.
How does nusinersen help in spinal muscular atrophy?
It is an antisense drug that changes SMN2 splicing so exon 7 is kept and more working SMN protein is made.
Why are many siRNA drugs linked to GalNAc?
Liver cells take up GalNAc, so the drug reaches the liver, where its target protein is made.
Connections
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Antisense (National Human Genome Research Institute (NHGRI), 2026); Gene Expression (National Human Genome Research Institute (NHGRI), 2026); What is gene therapy?: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.