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Messenger RNA

life science Maturity 9-11 Next article →

Messenger RNA, or mRNA, is a single-stranded molecule of RNA. It carries the genetic sequence of a gene to the cell's machinery. This molecule is essential for synthesizing proteins. This process is a key part of the central dogma of molecular biology. This term describes the flow of genetic information in a biological system. Without mRNA, the instructions in DNA could not be used to build life.

MRNA-interaction
MRNA-interaction

The life of an mRNA molecule begins with transcription. This is the process where genetic information is copied from DNA into RNA. An enzyme called RNA polymerase performs this job. The enzyme binds to a promoter sequence on the DNA. It then synthesizes a complementary RNA strand from the DNA template. During this step, the enzyme uses uracil instead of thymine. Uracil is placed opposite adenine bases on the DNA template. This ensures the genetic information is faithfully preserved.

DNA transcription
DNA transcription

In eukaryotes, the initial product is called precursor mRNA, or pre-mRNA. This molecule is not yet functional and requires extensive processing. First, a 5' cap is added to the front end of the molecule. This cap is a modified guanine nucleotide called 7-methylguanosine. The cap helps the ribosome recognize the mRNA. It also protects the molecule from being broken down by enzymes.

5' cap labeled
5' cap labeled

Next, the cell performs RNA splicing. This mechanism removes non-coding regions called introns. It joins the coding regions, known as exons, together. This creates a mature mRNA sequence.

Gene structure eukaryote 2 annotated
Gene structure eukaryote 2 annotated

Another vital step in eukaryotic processing is polyadenylation. This involves adding a poly(A) tail to the 3' end of the mRNA. An enzyme called polyadenylate polymerase adds about 150 to 250 adenosine residues. This tail helps protect the mRNA from degradation by exonucleases. It also aids in transcription termination and the export of the mRNA from the nucleus. In prokaryotes, polyadenylation works differently. In those organisms, poly(A) tails actually help facilitate the degradation of the RNA.

Polyadenylation
Polyadenylation

Once the mRNA is mature, it must move to the cytoplasm. In eukaryotes, the nucleus and cytoplasm are separated by a membrane. Mature mRNAs are recognized by specific proteins like CBP20 and CBP80. These proteins help the mRNA move through the nuclear pore. In some specialized cells, mRNA is transported to specific locations. For example, in mature neurons, mRNA can move from the soma to dendrites. Some mRNAs even use "zip codes" to reach their exact destination.

Fbioe-09-718753-g002
Fbioe-09-718753-g002

The final stage of the process is called translation. This is where the mRNA is read by a ribosome. The ribosome reads the nucleotide sequence in groups of three called codons. Each codon corresponds to a specific amino acid. Two other types of RNA are required for this step. Transfer RNA, or tRNA, recognizes the codon and provides the correct amino acid. Ribosomal RNA, or rRNA, is the main component of the ribosome's machinery.

Peptide syn
Peptide syn

Translation continues until the ribosome reaches a stop codon, such as UAG, UAA, or UGA.

The concept of mRNA was first proposed in 1960. Sydney Brenner and Francis Crick conceived the idea during a conversation with François Jacob. In May 1961, the existence of mRNA was experimentally proven. Two back-to-back papers were published in the journal Nature. One was by Brenner, Jacob, and Meselson. The other included James Watson and researchers named Gros. During this time, Jacob and Jacques Monod coined the term "messenger RNA."

MRNA structure
MRNA structure

Understanding mRNA connects many different biological ideas. It shows how information moves from a stable storage form to a functional product. The process involves complex interactions between enzymes, different types of RNA, and various cellular structures. From the transcription in the nucleus to the translation in the cytoplasm, every step is tightly regulated. This precise system ensures that cells build the exact proteins they need to function.

Fgene-10-00006-g001
Fgene-10-00006-g001
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🖼️ Images & Media (10)
File:MRNA-interaction.svg
MRNA-interaction.svg
File:DNA transcription.svg
DNA transcription.svg
File:Gene structure eukaryote 2 annotated.svg
Gene structure eukaryote 2 annotated.svg
File:5' cap labeled.svg
5' cap labeled.svg
File:Polyadenylation.png
Polyadenylation.png
File:Peptide syn.svg
Peptide syn.svg
File:MRNA structure.svg
MRNA structure.svg
File:Fbioe-09-718753-g002.jpg
Fbioe-09-718753-g002.jpg
File:Fgene-10-00006-g001.jpg
Fgene-10-00006-g001.jpg
File:1-s2.0-S1874939913000436-gr1 lrg.jpg
1-s2.0-S1874939913000436-gr1 lrg.jpg
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