The core process by which mRNA is synthesized is transcription. Overview
- Location: In eukaryotic cells, transcription occurs in the nucleus; in some viral systems or experimental in vitro setups, it can occur outside cells under cell-free conditions.
- Template: mRNA is produced using one strand of DNA as the template, in a 5' to 3' direction. The RNA polymerase reads the DNA template and builds a complementary RNA strand.
- Enzymes: The primary enzyme in eukaryotes is RNA polymerase II, which synthesizes pre-mRNA that often undergoes processing to become mature mRNA.
- Nucleotides: The building blocks are ribonucleoside triphosphates (ATP, GTP, CTP, UTP).
- Initiation, elongation, processing, termination:
- Initiation: Transcription factors help RNA polymerase locate a promoter and start RNA synthesis.
* Elongation: RNA polymerase adds nucleotides complementary to the DNA template, producing a growing mRNA chain.
* Processing (in eukaryotes): The primary transcript (pre-mRNA) is processed to become mature mRNA—this includes 5' capping, 3' polyadenylation, and splicing to remove introns.
* Termination: Transcription ends after RNA polymerase transcribes a termination signal; the mature mRNA is then exported to the cytoplasm for translation.
Key takeaways
- In most cellular contexts, mRNA synthesis is driven by RNA polymerase II and occurs in the nucleus, using DNA as the template.
- The resulting mRNA carries genetic information from DNA to ribosomes in the cytoplasm, where it guides protein synthesis.
If you’d like, I can tailor this to a specific organism (e.g., human cells) or explain the differences between transcription in prokaryotes versus eukaryotes.
