Post-transcriptional modification
Chemical alterations to RNA after transcription produce functional molecules.
Post-transcriptional modification is a set of biological processes common to most eukaryotic cells by which an RNA primary transcript is chemically altered after transcription to produce a mature, functional RNA molecule. These modifications are essential for the correct translation of eukaryotic genomes, as they convert precursor messenger RNA into mature mRNA capable of being translated into protein, and also process other transcripts such as transfer RNA and ribosomal RNA.
- field
- Molecular biology
- known_for
- Chemical alteration of RNA after transcription to produce functional RNA molecules
- processes
- 5' capping, 3' polyadenylation, RNA splicing
Lore & Background
Post-transcriptional modification includes three major steps that significantly alter the chemical structure of RNA: addition of a 5' cap, addition of a 3' polyadenylated tail, and RNA splicing. The 5' cap involves adding 7-methylguanosine to the 5' end, protecting the transcript from ribonucleases. RNA splicing removes introns and links exons, catalyzed by the spliceosome.
Reader's Guide
Post-transcriptional modification is vital for eukaryotic gene expression. The 5' cap and poly(A) tail facilitate mRNA transport to ribosomes and protect against degradation, while splicing removes non-coding introns to produce a continuous coding sequence. Alternative splicing allows production of multiple protein variants from a single gene. Histone mRNA processing differs, lacking poly(A) tails and introns, using a stem-loop structure instead. These modifications are fundamental to the diversity and regulation of the eukaryotic transcriptome.
Did You Know?
- The 5' cap is added via a 5'5' triphosphate link and can be methylated to form cap 0, cap 1, cap 2, or cap 3 structures.
- Nicotinamide adenine dinucleotide has been identified as a cap in plants, human, and yeast, possibly regulating gene expression via metabolites.
- Core histone mRNAs lack poly(A) tails and introns, and their 3' processing uses a stem-loop structure and U7 snRNA.
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