Post-Transcriptional Regulation
How cells control gene expression after transcription — by tuning mRNA stability, localisation, and translation, including silencing by small regulatory RNAs.
Definition
Post-transcriptional regulation is the control of gene expression at steps after transcription — governing the stability, localisation, and translation of mRNA — so that the amount and timing of protein production can be adjusted independently of transcription rate.
Scope
This topic covers regulation acting on the mRNA: control of transcript stability and decay, mRNA localisation, translational efficiency through factors and untranslated-region elements, and silencing by microRNAs and related small RNAs. It complements transcriptional and chromatin-level control by addressing the fate of the message itself; the broader biology of non-coding RNAs is developed in the RNA biology area.
Core questions
- How do cells control how long an mRNA persists before being degraded?
- How is the translation of an mRNA turned up or down?
- How do microRNAs silence their target messages?
- Why localise an mRNA to a particular part of the cell before translating it?
Key theories
- microRNA-mediated silencing
- Small RNAs base-pair with complementary sequences in target mRNAs, typically in their untranslated regions, to repress translation or promote decay, a mechanism first revealed by the lin-4 small RNA acting on lin-14.
- Control through untranslated regions and mRNA stability
- Elements in mRNA untranslated regions, recognised by proteins and small RNAs, set transcript half-life, localisation, and translational efficiency, providing a fast and reversible layer of expression control.
Mechanisms
The lifetime of an mRNA is set by its cap, poly(A) tail, and sequence elements that recruit stabilising or destabilising proteins, with deadenylation often triggering decay. Translation is regulated by initiation factors and by proteins or RNAs that bind untranslated regions to block or enhance ribosome recruitment. MicroRNAs, processed from precursors and loaded into silencing complexes, base-pair with target mRNAs to repress their translation and accelerate their degradation. Localisation signals direct certain mRNAs to specific cellular regions where they are translated on demand.
Clinical relevance
Dysregulated mRNA decay, translational control, and microRNA activity are implicated in cancers and other diseases, and small-RNA-based approaches are used as research and therapeutic tools; offered as significance, not clinical guidance.
History
The 1993 discovery by Ambros's and Ruvkun's groups that the lin-4 gene produces a small regulatory RNA controlling lin-14 introduced microRNA-mediated post-transcriptional control, which, with studies of mRNA stability and translational regulation, established this layer of gene expression.
Key figures
- Victor Ambros
- Gary Ruvkun
Related topics
Seminal works
- lee1993
- lodish2016
Frequently asked questions
- What is post-transcriptional regulation?
- Control of gene expression after an mRNA is made, by adjusting how stable it is, where it goes, and how efficiently it is translated.
- How do microRNAs reduce protein output?
- They base-pair with target mRNAs and recruit complexes that block translation and speed up degradation of the message, lowering the amount of protein produced.