mRNA

Messenger RNA (mRNA) is a single-stranded RNA molecule that conveys genetic information from DNA to the ribosome, where it specifies the amino acid sequence of a protein. In eukaryotes, mRNA transcripts are produced by RNA polymerase II and undergo processing before export to the cytoplasm. In prokaryotes, mRNA often lacks a nuclear processing step and can be translated immediately after transcription; bacterial mRNA may be polycistronic.

Most mature eukaryotic mRNAs possess a 5' cap, a 5' untranslated region, a protein-coding sequence, a 3' untranslated region, and a poly(A) tail. The cap and tail, along with regulatory elements in the UTRs, influence stability and translation efficiency. Splicing may remove introns to produce a continuous coding sequence.

During translation, the ribosome reads codons to recruit cognate tRNAs and synthesize a polypeptide. Initiation in eukaryotes requires a 5' cap and poly-A tail and initiation factors; prokaryotic initiation relies on a Shine-Dalgarno sequence. Translation occurs in the cytoplasm and often involves polysomes.

mRNA turnover is governed by deadenylation, decapping, and exonucleolytic decay, with various surveillance pathways such as nonsense-mediated decay recognizing faulty transcripts. The half-life of mRNA varies widely and is influenced by sequence elements and binding proteins.

mRNA has become a key tool in research and medicine. Synthetic mRNA, produced by in vitro transcription, encodes specific proteins and is delivered to cells using lipid nanoparticles or other vectors; this approach underlies mRNA vaccines and therapeutic strategies. Nucleoside modifications can reduce innate immune sensing and increase stability.